WEBVTT 1 00:00:00.480 --> 00:00:00.719 Mark Kushner: you're. 2 00:00:01.979 --> 00:00:16.529 Mark Kushner: still take to take to get it so it's a great pleasure to welcome us to do tomorrow of Ohio State of Ohio the Ohio State University, as our first missy seminar speaker this year. 3 00:00:18.029 --> 00:00:19.650 Mark Kushner: Blue got his PhD. 4 00:00:21.300 --> 00:00:33.780 Mark Kushner: And then was at bell labs and labs was kind of what the labs and then brookhaven and in 2004 he. 5 00:00:36.000 --> 00:00:47.790 Mark Kushner: went to Ohio State University and is now the doctor Professor current the fellow vs was a triple as. 6 00:00:49.350 --> 00:00:50.700 Mark Kushner: A couple years ago. 7 00:00:52.080 --> 00:00:53.310 Mark Kushner: On the shallow. 8 00:00:54.420 --> 00:00:55.350 Mark Kushner: prize for. 9 00:00:56.370 --> 00:00:59.130 Mark Kushner: physics so just talk today. 10 00:01:00.360 --> 00:01:02.340 Mark Kushner: we're scaling because laser. 11 00:01:03.780 --> 00:01:04.740 Mark Kushner: Okay, thank you call. 12 00:01:07.560 --> 00:01:13.830 Mark Kushner: I want to thank mark for the invitation here and I guess i'm honored to be the first. 13 00:01:15.300 --> 00:01:21.870 Mark Kushner: Speaker of the the new semester, and also the first guinea pig have been in person set correct. 14 00:01:23.340 --> 00:01:24.300 Mark Kushner: thanks for that on. 15 00:01:25.440 --> 00:01:25.860 Mark Kushner: So. 16 00:01:27.180 --> 00:01:28.800 Mark Kushner: This literally is the first. 17 00:01:30.030 --> 00:01:31.410 Mark Kushner: Talk i'm given in person. 18 00:01:32.730 --> 00:01:35.130 Mark Kushner: Monday night I gave a talk in Shanghai. 19 00:01:36.330 --> 00:01:42.990 Mark Kushner: have had a PM at night cove resume and or my whole life has been in zoom including my teaching. 20 00:01:44.130 --> 00:01:55.530 Mark Kushner: So it's a pleasure to be here and I have a long history of collaborating with the University of Michigan, especially the people here in engineering. 21 00:01:56.640 --> 00:01:57.060 Mark Kushner: So. 22 00:01:58.380 --> 00:02:15.180 Mark Kushner: What I wanted to discuss today is scaling up strong field physics and i'll describe strong feel physics in in you know my definition of strong feelings, you know that that means different things to different people. 23 00:02:17.280 --> 00:02:17.670 Mark Kushner: and 24 00:02:18.810 --> 00:02:30.810 Mark Kushner: The scaling I particularly want want to talk about is something that occupies my thinking now for over two decades is the wavelength scaling a strong field with directions. 25 00:02:32.100 --> 00:02:42.960 Mark Kushner: So I want to talk about two extremes one extreme, which I know a lot more about and i'll tell you a lot more about in your hopefully walk away. 26 00:02:44.490 --> 00:02:50.640 Mark Kushner: Knowing a lot more about is the low frequency limit a strong field interactions okay. 27 00:02:52.110 --> 00:03:02.790 Mark Kushner: Then the last part will be more speculative asking the question where is the strong field in the X Ray machine now how possibly does it scale there. 28 00:03:03.570 --> 00:03:15.870 Mark Kushner: Okay here you'll leave just scratching your head Okay, but I hope to kind of intrigued you with this possibility of thinking about strong fields that are very high frequency. 29 00:03:17.340 --> 00:03:29.640 Mark Kushner: and hopefully motivate some of you to think about this in the future, because the technology is starting to catch up in terms of being able to take about short field in the X Ray machine. 30 00:03:31.260 --> 00:03:34.470 Mark Kushner: So I want to spend the time. 31 00:03:35.640 --> 00:03:51.930 Mark Kushner: Talking about the low frequency rishi now, you might my definition of this interaction is, I have an atom and I shine in intense pulse of light upon it Okay, and that has been going on since almost. 32 00:03:53.430 --> 00:03:58.860 Mark Kushner: The laser has was invented Okay, and so the majority of. 33 00:04:06.150 --> 00:04:06.810 Mark Kushner: that's not good. 34 00:04:09.570 --> 00:04:11.280 Mark Kushner: Well, mark you have your song. 35 00:04:29.310 --> 00:04:30.750 Mark Kushner: Okay, thank. 36 00:04:33.270 --> 00:04:34.980 Mark Kushner: So yeah I mean these type of. 37 00:04:37.890 --> 00:04:45.630 Mark Kushner: You know ideas of looking at lasers interacting with matter in a strong field contact been going on almost since the. 38 00:04:47.220 --> 00:04:59.760 Mark Kushner: discovery of the laser Okay, but the majority of those studies in, say, the last three decades have mainly been confined to like one micron or. 39 00:05:00.300 --> 00:05:14.160 Mark Kushner: or 0.8 microns okay and, and the reason for that is simply that's where our best lasers, are those lasers, we can extract large amounts of energy and we can produce that light pulse. 40 00:05:14.850 --> 00:05:25.260 Mark Kushner: In in a very short amount of time, so the experiments will be dictated by the best lasers in those best leaders have served us well. 41 00:05:26.250 --> 00:05:45.000 Mark Kushner: But that's not the claim that the best ways is necessarily the best laser for science and and and and that's what was you know drive from my curiosity, is how does this physics behaviors I I changed the wavelength, I mean you know we've been taught. 42 00:05:46.170 --> 00:06:05.760 Mark Kushner: To think about these processes that I study are extremely nonlinear in many ways, or non resident, so why does the main the wavelength matter at all i'll try to show you that matters a great deal in terms of making energetic particles and energetic photons. 43 00:06:07.680 --> 00:06:08.580 Mark Kushner: Okay, so. 44 00:06:10.320 --> 00:06:12.360 Mark Kushner: In the last decade, I would say. 45 00:06:13.410 --> 00:06:26.250 Mark Kushner: The landscape in terms of the best place has been like near ir is changing, and particularly at the longer wavelength, the type of work that's going on here at Michigan and. 46 00:06:27.300 --> 00:06:32.910 Mark Kushner: We started to exploit some of these techniques to make posters that long wavelength. 47 00:06:33.360 --> 00:06:44.310 Mark Kushner: So you know in my simple mind I was thinking is like the physics, has to be different if I go to the DC limit Okay, so I wanted to hit the DC limit and. 48 00:06:45.090 --> 00:06:59.670 Mark Kushner: And, and so that's what i'll tell you about then i'll end up talking about how this physics, according to the metrics that i'm going to introduce to you will scale to very high frequency. 49 00:07:00.810 --> 00:07:05.400 Mark Kushner: And then I went by telling you that I think that's nonsense that what i'll say. 50 00:07:08.280 --> 00:07:08.700 Mark Kushner: Okay. 51 00:07:10.230 --> 00:07:10.710 Mark Kushner: So. 52 00:07:12.480 --> 00:07:24.180 Mark Kushner: We in a bunch of people and some of the people here at Michigan were funded by the air force in one of these Murray projects, the mural project ended this year. 53 00:07:25.350 --> 00:07:28.350 Mark Kushner: And the idea was to explore. 54 00:07:29.760 --> 00:07:39.930 Mark Kushner: explore how many infrared radiation can be used to study things from very basic physics like I show here. 55 00:07:41.400 --> 00:07:49.830 Mark Kushner: harmonic radiation from a solid two more apply things like How does this mean infrared this intense mid infrared. 56 00:07:50.400 --> 00:08:03.090 Mark Kushner: Radiation propagate through the atmosphere, or can the MID infrared radiation be advantage for thinking about things like electron or Ion acceleration. 57 00:08:03.540 --> 00:08:15.390 Mark Kushner: And those ideas will based upon simple scaling parameters that said that if I push the longer wavelength, I would indeed gain some benefits from it. 58 00:08:20.070 --> 00:08:21.900 Mark Kushner: So let me tell you about. 59 00:08:23.190 --> 00:08:28.590 Mark Kushner: Where it kind of started with me again i'm an atomic physicists not a plasma physicists. 60 00:08:30.540 --> 00:08:36.570 Mark Kushner: So my my my ideas were grounded in more kind of fundamental atomic interactions. 61 00:08:38.250 --> 00:08:47.220 Mark Kushner: So I started to worry about this problem of scaling, and so we went ahead and did a calculation okay so you're seeing the result of a calculation. 62 00:08:48.240 --> 00:09:00.420 Mark Kushner: And this is a calculation, so when you interact an atom with intense radiation, one of the outcomes of that strong interaction is the generation of high harmonic radiation. 63 00:09:00.900 --> 00:09:16.680 Mark Kushner: Okay hi harmonic radiation is just a cone of odd harmonics that a key stand or the very high energy, so you, you know you pump it at one micron and you get out so effects rates a coma soft X rays. 64 00:09:17.460 --> 00:09:27.690 Mark Kushner: And so, this calculation is looking at that, and what is it looking at is the time history of the mission of this high harmonic radiation. 65 00:09:29.160 --> 00:09:33.150 Mark Kushner: planet is a function of the frequency, so what you see here. 66 00:09:34.800 --> 00:09:48.330 Mark Kushner: Is the contour plot or a quantum calculation Okay, and the solid lines are based on just some classical physics okay just newton's equations. 67 00:09:48.990 --> 00:10:02.640 Mark Kushner: And if you look at the two you notice that the quantum system has similarities to the classical behavior but obviously the quantum system is much more complex, I mean you have all these. 68 00:10:03.270 --> 00:10:11.610 Mark Kushner: quantum we're launching all these quantum wave packets and they're interfering with each other and you see lots of interference in the in that contour plot. 69 00:10:13.290 --> 00:10:16.320 Mark Kushner: So the classical view seem to. 70 00:10:18.840 --> 00:10:29.400 Mark Kushner: mimic somewhat the quantum behavior and this calculation is done using an 800 assuming I have an 800 nanometers drive and field, titanium sapphire. 71 00:10:30.660 --> 00:10:37.680 Mark Kushner: Now I do the same calculation same intensity everything's the same, the only thing I do is change. 72 00:10:38.730 --> 00:10:42.900 Mark Kushner: The wavelength from point A to two microns so the MID infrared. 73 00:10:43.920 --> 00:10:46.200 Mark Kushner: And what you notice now is that the. 74 00:10:47.700 --> 00:10:53.010 Mark Kushner: quantum and the classical result is almost indistinguishable. 75 00:10:54.180 --> 00:10:59.730 Mark Kushner: So the quantum system could be well approximated by a classical model. 76 00:11:00.750 --> 00:11:06.660 Mark Kushner: Okay, and this is important right, I mean because the classical physics, is a lot more easier. 77 00:11:08.550 --> 00:11:13.410 Mark Kushner: To visualize, then the all the quantum interference, excuse me. 78 00:11:15.960 --> 00:11:32.820 Mark Kushner: So this motivated us a great deal that moving towards these long or wavelengths had the benefits we were looking for, so our question was what do we need to do to get to this kind of classical behavior out of my quantum system. 79 00:11:35.670 --> 00:11:52.710 Mark Kushner: So let me define the strong field in the context of my work so it's the cool long gauge that determines the strong field, for me, so I just looked at the electric field associated with the electrons and protons in the ground state of hydrogen. 80 00:11:54.240 --> 00:11:55.440 Mark Kushner: calculate that field. 81 00:11:56.520 --> 00:12:18.330 Mark Kushner: That field is 1050 volts francs from, and now I asked myself what laser field Do I need to lead to an equivalent electric field and, again, you just use simple calculation, then you find that you need three times 10 to the 16 Watts per centimeter Square. 82 00:12:19.590 --> 00:12:40.470 Mark Kushner: Thank you degenerate a field of 50 volts French so that's the equivalent laser field of atomic unit of field Okay, so in our interest were interested in working in the regime where this where our imposed field. 83 00:12:41.700 --> 00:12:43.530 Mark Kushner: is comparable to that of the cool on. 84 00:12:45.420 --> 00:12:48.870 Mark Kushner: And this is very different than, say, which done here. 85 00:12:50.010 --> 00:13:01.620 Mark Kushner: In cubicles where they're talking about orders of magnitude beyond that, so that that's another point that should make this intensive tend to the 60 Watts per centimeter Square. 86 00:13:02.130 --> 00:13:12.090 Mark Kushner: Is a trivial field to achieve in the laboratory Okay, the best laces exceed that by six $7 and 90 so there's no challenge there. 87 00:13:15.810 --> 00:13:17.310 Mark Kushner: Okay once I have this. 88 00:13:18.960 --> 00:13:33.300 Mark Kushner: For you this gauge the question is, what happens if I just put an electron in that field free electron so again i'm just doing classical mechanics I write down F equals ma and solve those equations. 89 00:13:34.590 --> 00:13:37.740 Mark Kushner: And I can derive to quantities. 90 00:13:39.120 --> 00:13:43.530 Mark Kushner: of interest Okay, I have a linear polarized field that have an electron. 91 00:13:44.640 --> 00:14:00.060 Mark Kushner: The light field is put on to the electronic electronic machine might imagine just quivers in that field So the first thing I can ask is what is cycled average energy of the quiver and then how much displacement does the. 92 00:14:01.980 --> 00:14:15.180 Mark Kushner: electron have in that field Okay, so I can derive that quiver energy that quiver energy is the or the pond amount of energy, you see, is proportional to Lambda squared times the intense. 93 00:14:15.630 --> 00:14:27.960 Mark Kushner: So it's more strongly dependent on the wavelength there's no other quantities in this except the charge of the electron and the mass of the electron right that's it there's no atomic physics, in a tour field. 94 00:14:28.770 --> 00:14:43.200 Mark Kushner: Okay, the displacement, you can see, also scales, as the wavelength squared, but in this case it's linear in the electric field, not the intense square root of intensity so let's put numbers to that. 95 00:14:45.030 --> 00:14:59.010 Mark Kushner: So i'm going to come always use the tie sapphire is by point, the comparison so i'm doing this calculation for pointing in a two micron field at one terawatt per centimeter square so i'm even below this atomic unit of field. 96 00:15:00.180 --> 00:15:02.130 Mark Kushner: by at least an order of magnitude. 97 00:15:03.240 --> 00:15:12.720 Mark Kushner: And you can see the Panda motor potential is 60 ev full time staff, I made 360 ev for. 98 00:15:13.680 --> 00:15:25.350 Mark Kushner: The two micron field now think about the binding, I have a felony electron the Valence electron is only bound by 10 to 20 feet, so this potential is significant. 99 00:15:25.740 --> 00:15:36.870 Mark Kushner: respect to just the binding of the electrons in matter and, if you look at the displacement displacement of electron is 25 banks rooms at 800. 100 00:15:37.320 --> 00:15:55.740 Mark Kushner: And it's up to 158 mushrooms in this two micron field Okay, think about the size of the ground state of an atom right it's a half financial Okay, so this is again a scale that overwhelms the kind of atomic dimensions. 101 00:16:00.210 --> 00:16:06.180 Mark Kushner: Okay, so I want you to kind of think in these Panda motiva quiver units because. 102 00:16:07.830 --> 00:16:29.850 Mark Kushner: Always what's beautiful in physics is finding that there's a certain way of looking at scale and that becomes invariant and when you start looking at kind of the results of these interactions in these ponder mode of units you'll see that they basically start all looking the same okay. 103 00:16:31.980 --> 00:16:35.670 Mark Kushner: Let me say it another way, this field is so strong. 104 00:16:37.140 --> 00:16:42.990 Mark Kushner: Okay, this motion is so dominant that all it depends upon is the field, the first order. 105 00:16:44.520 --> 00:16:48.480 Mark Kushner: And the details of the atom doesn't matter second order effects. 106 00:16:50.520 --> 00:16:50.880 Mark Kushner: Okay. 107 00:16:52.260 --> 00:16:56.640 Mark Kushner: So we do the experiments, but of course we don't have free electrons we have atoms. 108 00:16:57.870 --> 00:17:01.890 Mark Kushner: And so, how do we get the free electron well you for the wind is it. 109 00:17:03.720 --> 00:17:06.630 Mark Kushner: And there's different ways of thinking about photo ionization. 110 00:17:07.770 --> 00:17:09.240 Mark Kushner: In that was a. 111 00:17:10.500 --> 00:17:12.900 Mark Kushner: What wasn't first proposed, but at least. 112 00:17:15.300 --> 00:17:32.670 Mark Kushner: was taught about by cal dish back in the early 60s again with the invention of the laser effect, I was surprised to learn as we buy colleague and I PR agassi we're looking at kill, this is famous paperback and 63 the first reference. 113 00:17:33.900 --> 00:17:44.130 Mark Kushner: was an experiment done in the engineering department at Ohio State University by two people that no one has any knowledge, who they were they were obviously some faculty and engineering. 114 00:17:44.610 --> 00:17:54.600 Mark Kushner: And it appeared what they had this they had one of the first movie laces they got the Ruby laser put a lens in front of it focused it in air broke down air. 115 00:17:55.620 --> 00:18:02.130 Mark Kushner: published a paper on that and kill the fish use that as motivation for working on his. 116 00:18:03.420 --> 00:18:05.400 Mark Kushner: organization in the DC limit. 117 00:18:06.630 --> 00:18:18.240 Mark Kushner: So it's kind of odd but would they kill this say so kill the says what matters in the dynamics that drive the system is the ratio this dimensional ratio. 118 00:18:19.320 --> 00:18:30.420 Mark Kushner: gamma known as we call it the kelvin parameter is the ratio of the optical frequency to the tonally frequency so totally frequency is kind of weird concept. 119 00:18:31.260 --> 00:18:39.060 Mark Kushner: it's controversial that started people to start thinking about tunneling times in the end, over the last several decades. 120 00:18:39.900 --> 00:18:56.130 Mark Kushner: But in either case, this is how he framed his model thinking about that, and what he showed this that you can write this at a big city parameter in in terms of just the ionization potential of the atom. 121 00:18:58.110 --> 00:19:14.250 Mark Kushner: And the field through the power of the mode of energy, and therefore this gamma parameter scales is one over the wavelength, or one over the square root of the intensity and we tell the says that if this number gamma is small, less than one. 122 00:19:15.630 --> 00:19:26.430 Mark Kushner: In the limit of zero, which is DC Okay, then I have a potential in an electric field it's a stock potential the electron has some probability of. 123 00:19:27.120 --> 00:19:34.470 Mark Kushner: of tunnel lionizing into the continuum and if I told you okay i'll hook it up to some type of rf. 124 00:19:35.460 --> 00:19:45.690 Mark Kushner: power supplies at 60 hertz and I start rocking that potential back and forth that 60 hertz you would still say oh yeah there's still enough time for the electron. 125 00:19:46.140 --> 00:19:56.580 Mark Kushner: To tunnel through that barrier so tongue is still valid, but how about the optical rishi right where are my my potential is rocking back and forth very rapidly. 126 00:19:57.120 --> 00:20:08.460 Mark Kushner: Is that still a valid pitcher well we usually think in the optical regime of ionization is the current through so option of photons it's a cycle, the average process right. 127 00:20:09.420 --> 00:20:18.000 Mark Kushner: But Kelly says, as long as this parameter is less than one does it matter what regime of the electromagnetic spectrum you're at. 128 00:20:19.140 --> 00:20:26.160 Mark Kushner: Okay, so this cartoon here is supposed to demonstrate that for high intensities. 129 00:20:27.990 --> 00:20:40.800 Mark Kushner: You go into this DC picture of ionization or at low frequency has one heads to zero frequency you're in this tunneling machine as the frequency goes up. 130 00:20:41.430 --> 00:20:53.070 Mark Kushner: This photon picture is more appropriate was the density drops this photon picture is appropriate, and that is the limit of gamma created one. 131 00:20:54.060 --> 00:21:13.830 Mark Kushner: Okay, so that's the element so cal dishes given us a way of thinking about how the electron escapes into the kitchen, you want to get into the continuum I know the answer is just newton's equations right, but then the electron is just going to quiver in that field okay. 132 00:21:16.050 --> 00:21:39.120 Mark Kushner: Now there's another important aspect here, which I won't stress a great deal is that in order for me to connect that newtonian mechanics to the mode of organization, I need to think deterministic Lee about when the electron one into the continue so I have a field. 133 00:21:40.350 --> 00:21:41.100 Mark Kushner: it's not good. 134 00:21:54.720 --> 00:21:55.950 Mark Kushner: just give me a second. 135 00:22:02.730 --> 00:22:03.120 Mark Kushner: Okay. 136 00:22:04.500 --> 00:22:16.980 Mark Kushner: So I need to think about a phase, at which the electron was released in the field, and then I just apply newtonian mechanics Okay, so what happens when I released the electron in the field. 137 00:22:17.880 --> 00:22:24.990 Mark Kushner: It quivers like we said and dependent upon the phase of the field it picks up a drift velocity. 138 00:22:25.530 --> 00:22:37.590 Mark Kushner: what's the drift velocity the drift velocity is just the vector potential at the time the electron is is created, so the electron tunnels into the field okay. 139 00:22:38.520 --> 00:22:49.680 Mark Kushner: At some phase of the field, which has an associated fact the potential and the electron gets a kick from the vector potential so not only does it quiver it also drifts. 140 00:22:50.520 --> 00:22:58.200 Mark Kushner: Okay, and that's a constant of the motion Okay, when the field is over the quiver is gone, but the electronic drifting out to a Judas. 141 00:22:59.820 --> 00:23:10.620 Mark Kushner: Okay, so these elements put together led to this cartoon Okay, and the cartoon has been vetted very carefully, since the early 90s. 142 00:23:11.580 --> 00:23:21.630 Mark Kushner: it's called the rich scattering or three step models, the elements of simple I tunnel, so now, I have this deterministic view. 143 00:23:22.470 --> 00:23:33.150 Mark Kushner: Of phase and, once it tells all I do is propagated, that is, the quiver and then allow the electron to come back and interact with its own core. 144 00:23:33.690 --> 00:23:46.170 Mark Kushner: So you might imagine it's easy the show demonstrate classically that some electrons do this they quiver and drift away from the core, but certain trajectories do this. 145 00:23:46.920 --> 00:23:57.330 Mark Kushner: and return and then quiver in the opposite direction it's that event right that event is like an electron accelerator. 146 00:23:58.020 --> 00:24:04.560 Mark Kushner: On the nanometers scale that's important enormous energy into the electron and when it returns. 147 00:24:05.190 --> 00:24:22.980 Mark Kushner: And interacts with its own core can do a number of things, it can emit a photon but that full time is much higher energy, then the field right the article feel that rocking back and forth, it can elastic we scatter which means now I can pick up additional. 148 00:24:24.120 --> 00:24:32.640 Mark Kushner: Energy into the electron by rescheduling or it can elastic Lee scattered, that is, it can come back and knock or more electrons off. 149 00:24:34.320 --> 00:24:47.190 Mark Kushner: Okay, so that's the picture and it's a classical picture or semi classical the semi part is totally totally is quite them phenomena Okay, but everything else is new newtonian mechanics and. 150 00:24:48.360 --> 00:25:00.210 Mark Kushner: What you find this since the classical model, you can determine certain quantities like what is the maximum energy that electronic can have when it returns to the core well you do the math. 151 00:25:00.660 --> 00:25:11.670 Mark Kushner: And you find out it's 3.17 times upon the most advantage okay that's a hard number that's the maximum number, so if the electronic comes back. 152 00:25:12.390 --> 00:25:30.720 Mark Kushner: And emits a photon the highest energy photon is going to be 3.17 up plus whatever the binding energy was OK so it's known that harmonics is some i'd say told you about they form a plateau and then they cut off and they cut off. 153 00:25:31.830 --> 00:25:41.070 Mark Kushner: And essentially three up Okay, and we already saw that, based on the wavelengths you're using up is enormous. 154 00:25:42.300 --> 00:25:56.220 Mark Kushner: OK, so the binding energy is only 1020 volts, but I can have panic mode of energies up to 100 volts, which means the photons could be 300 volts so the IP doesn't even matter in the sense. 155 00:25:57.510 --> 00:25:57.930 Mark Kushner: Okay. 156 00:26:02.070 --> 00:26:17.730 Mark Kushner: Yes, the elastic scattering could lead to this additional energy out the 10 up, so we have real classical predictions of where things should be according to the semi classical physics, the key is that. 157 00:26:19.410 --> 00:26:22.740 Mark Kushner: We are in the low frequency limit. 158 00:26:23.820 --> 00:26:31.230 Mark Kushner: Right and that's what's the motivation of why we were exploring into the MID infrared. 159 00:26:32.250 --> 00:26:35.490 Mark Kushner: Now one thing, yes, one electron. 160 00:26:37.230 --> 00:26:37.440 Mark Kushner: yeah. 161 00:26:38.490 --> 00:26:40.380 Mark Kushner: Well, this is a class this cartoon. 162 00:26:42.690 --> 00:26:44.640 Mark Kushner: that's right, we can accurately predict. 163 00:26:46.440 --> 00:26:49.530 Mark Kushner: Like ionization of interfaces in the strong view. 164 00:26:51.000 --> 00:26:55.320 Mark Kushner: within a single active electron approximation it works very well. 165 00:26:55.710 --> 00:27:14.040 Mark Kushner: And we can discuss why it is, but in inner gases, the separation of the ground state from the first day excited state is almost the entire binding energy of the ground state, so the majority of the process is driven through a very non resident process OK so. 166 00:27:15.990 --> 00:27:23.520 Mark Kushner: The single electronic it seems like you're only you just move even though you know you have this close show Adam. 167 00:27:25.050 --> 00:27:30.570 Mark Kushner: You might think you excited a number of them, but in fact you're only exciting one, at a time, the first order. 168 00:27:35.070 --> 00:27:48.210 Mark Kushner: Okay, so let's look at some of these scaling parameters that we have used, we already looked at the kill dish we saw that the kill this again gamma get smaller the long and the wavelength. 169 00:27:49.290 --> 00:27:52.530 Mark Kushner: makes sense, the part of the mode of energy. 170 00:27:53.910 --> 00:28:05.490 Mark Kushner: leads to higher energy that goes quadratic with the wavelength so there's two advantages in the context of this kind of semi classical model is long wavelengths. 171 00:28:06.540 --> 00:28:09.510 Mark Kushner: promote tunneling which you want and. 172 00:28:11.580 --> 00:28:16.230 Mark Kushner: It puts more energy and to electron destroys the high energy particles. 173 00:28:17.700 --> 00:28:40.050 Mark Kushner: In terms of making short pulses this dispersion it's a funny dispersion i'll show you about what we call the apple church so it's kind of like a trip in your CPA laser the aperture also has a favorable scaling wavelength longer wavelength leads to shorter at the second pulses. 174 00:28:41.880 --> 00:28:46.020 Mark Kushner: But I want to now emphasize our strategy, one more time using. 175 00:28:47.490 --> 00:28:51.210 Mark Kushner: A more complete set of metrics okay so. 176 00:28:52.230 --> 00:29:02.070 Mark Kushner: These authors crown or recent smirnoff introduced these ideas of what they call bound and continuum intensity parameters. 177 00:29:03.120 --> 00:29:09.840 Mark Kushner: To see one parameter, which is the bound parameter could be recast in terms of cal dishes theory okay. 178 00:29:11.340 --> 00:29:15.120 Mark Kushner: The point I want to make here is that the bounced a parameter. 179 00:29:16.170 --> 00:29:17.310 Mark Kushner: scales as Lambda. 180 00:29:19.140 --> 00:29:20.670 Mark Kushner: Lambda squared i'm sorry. 181 00:29:22.380 --> 00:29:25.560 Mark Kushner: it's hard to see with this fog and in my glasses. 182 00:29:27.960 --> 00:29:30.150 Mark Kushner: And plus my eyesight it's not that great either. 183 00:29:33.210 --> 00:29:48.690 Mark Kushner: And you should think about the bounce state parameter as the point at which the ground state say that's your initial state distorts due to the presence of this field, and how does it distort it distorts into this stock like potential right where. 184 00:29:49.890 --> 00:29:58.710 Mark Kushner: it's no longer bound or it's bound, but it has some probability of just telling it to the continuum so that that's the story. 185 00:30:00.300 --> 00:30:01.020 Mark Kushner: Ground state. 186 00:30:02.280 --> 00:30:06.120 Mark Kushner: The continuum intensity parameter, you could see scales as lamb the cube. 187 00:30:07.920 --> 00:30:25.980 Mark Kushner: And that just measures, the pan, the mole advantage relative to the photon energy so let's think back to that two micron case that we talked about the earlier, the example that we had one patois and I think we said that the Panda mode of energy was 360 volts. 188 00:30:27.270 --> 00:30:29.880 Mark Kushner: Okay, the full time, energy, in that case. 189 00:30:31.020 --> 00:30:35.700 Mark Kushner: For two microns is like Point six ED right it's a kind of. 190 00:30:37.170 --> 00:30:44.280 Mark Kushner: Very counterintuitive way of thinking, if I want more energy out of my articles, I need small photons. 191 00:30:45.870 --> 00:30:58.830 Mark Kushner: thing you think about a little harder you say oh that makes sense because the smaller the photons the long period and the more time the electron Spencer, the beans accelerated by the field. 192 00:31:00.510 --> 00:31:00.870 Mark Kushner: Okay. 193 00:31:02.640 --> 00:31:12.390 Mark Kushner: So let's look at these parameters, so he is my definition of a strong field which is again the REACH that what I either call the strong field women or the kelvin women. 194 00:31:13.440 --> 00:31:20.850 Mark Kushner: Is that gamma according to kill, this must be less than one and both PC parameters must be must be much greater than one. 195 00:31:23.550 --> 00:31:37.200 Mark Kushner: Okay, so just to let you guys know, during the course of the last two decades, we have manipulated sources that worked from like one to four and a half microns and that's what we've been using. 196 00:31:38.550 --> 00:31:45.840 Mark Kushner: These different flavors of how we do that so here's a picture now what i'm plotting is. 197 00:31:47.190 --> 00:31:49.890 Mark Kushner: The frequency versus intensity. 198 00:31:51.210 --> 00:31:58.410 Mark Kushner: And i'm doing that setting the Z parameter is equal to one, so the solid lines are just one Z equals one. 199 00:31:59.820 --> 00:32:12.180 Mark Kushner: Okay, and I just plugged in So this is the hydrogen atom so there's you know delphine the binding energy and then i'm just plugging in the calculate the intensity and frequency behavior. 200 00:32:13.410 --> 00:32:17.490 Mark Kushner: So here we are here, we are working with titanium sapphire later. 201 00:32:18.540 --> 00:32:25.800 Mark Kushner: Okay, and what I started doing this, you know, I have a knob now start turning up the intensity of my laser and as i'm. 202 00:32:26.370 --> 00:32:35.730 Mark Kushner: Increasing the intensity on this scale what's happening is you know if i'm calculating this perturbation theories working very well, I can express it in that way. 203 00:32:36.180 --> 00:32:41.490 Mark Kushner: But at some point they start noticing that the behavior of the system becomes non paternal. 204 00:32:41.970 --> 00:32:50.160 Mark Kushner: and eventually I reach a point where the continuum is distorting that is that the part of the motivation, she is greater than the photon energy. 205 00:32:50.940 --> 00:33:00.780 Mark Kushner: Okay, and at that point, I have this electron that's being promoted by some ionization and it started the quiver once it's free. 206 00:33:01.650 --> 00:33:06.540 Mark Kushner: Okay, and eventually as I increase the intensity I crossed this. 207 00:33:07.530 --> 00:33:24.540 Mark Kushner: bounce fade intensity parameter, and at that point, the ground state stored and the electron is now totally continue and that's exactly where I want to be, I want to be sitting somewhere here in order to validate the semi classical model. 208 00:33:26.040 --> 00:33:29.850 Mark Kushner: Now why, can I just turn up the intensity like I just described to you. 209 00:33:31.710 --> 00:33:36.540 Mark Kushner: Remember, this is extremely nonlinear physics tunneling, as you know. 210 00:33:38.160 --> 00:33:45.570 Mark Kushner: It has a rate that is exponential in the field Okay, so if I have an atom sitting there on the ground state. 211 00:33:46.710 --> 00:34:03.450 Mark Kushner: Just a small change in the intensity the atom is gone everything's in the continue so the visibility and intensity, the control of intensity is a very narrow parameter in which for me to control these organizations dynamics. 212 00:34:05.700 --> 00:34:15.270 Mark Kushner: But if I just changed the wavelength like that arrow just did I now move to a regime where I can get into this boundaries bound. 213 00:34:16.980 --> 00:34:21.450 Mark Kushner: distortion and still not need. 214 00:34:23.100 --> 00:34:26.040 Mark Kushner: An enormous amount of intensity more importantly. 215 00:34:27.570 --> 00:34:36.990 Mark Kushner: The wave went knobs continuous right, I can tune this arrow wherever I want by just changing the wavelength okay I can't do that but intensity. 216 00:34:41.970 --> 00:34:49.740 Mark Kushner: is really becoming hard with this so let's look at some classical trajectories just to get a feel for what's up so again. 217 00:34:50.460 --> 00:35:01.020 Mark Kushner: This is just we assume the electronic tunnels to you i'm not doing the calculation, the i'm just going to drop it in the field at some phase of the field that's where tunnel okay. 218 00:35:01.560 --> 00:35:14.070 Mark Kushner: And then use newton's equations and calculate your checklist so here we're plotting position versus time Okay, the Red dotted line is the optical field okay. 219 00:35:15.210 --> 00:35:25.350 Mark Kushner: What i'm going to do is drop the electron in the field at this phase of the field Okay, so now it's going to pick up a quiver and adrift. 220 00:35:26.520 --> 00:35:37.140 Mark Kushner: Okay, the drift is just determined by the potential of the field so now what you see what this trajectory does it propagates away from the core. 221 00:35:37.770 --> 00:35:52.170 Mark Kushner: And then comes back to it, because the drift the pose the initial motion OK, and now it comes back and it interacts Okay, so let me calculate the instantaneous kinetic energy upon return. 222 00:35:53.190 --> 00:35:58.440 Mark Kushner: And I get that out there doesn't matter what that data is that that is one times upon them all advantage. 223 00:35:59.820 --> 00:36:13.980 Mark Kushner: Okay, what i'm going to do is now launch a few more reject reach three more just by changing their face the initial condition is the same, I assume that the initial energy of the electronic the continuum is zero. 224 00:36:15.300 --> 00:36:25.650 Mark Kushner: What seems like a pretty good approximation for a ton of line is he you know the electronic find the cell phone the outer turning points have the potential to sit there in the field, etc. 225 00:36:27.960 --> 00:36:40.950 Mark Kushner: OK, so now, you see those trajectories and what you notice is that those trajectories propagated are graded distance than the original one and plus they return that a different time. 226 00:36:42.180 --> 00:36:50.070 Mark Kushner: And when they return that a different time they gave it had a different instantaneous return energy and that's plotted here. 227 00:36:51.840 --> 00:36:53.790 Mark Kushner: And what you notice there's a slope to that. 228 00:36:55.140 --> 00:37:07.500 Mark Kushner: So, therefore, the return any cheese chirped in this case it's shirt in a normal way right like a normal dispersion Okay, the reds. 229 00:37:09.090 --> 00:37:20.280 Mark Kushner: yeah someday I will change the color coding here, but the reds come before the blues and the blues of red and the reds a blue okay. 230 00:37:22.080 --> 00:37:26.700 Mark Kushner: So this is a positive chirp I think about it as dispersion and. 231 00:37:27.750 --> 00:37:43.290 Mark Kushner: Great I have a dispersion there, it looks pretty linear to funny dispersion again, this is the dispersion of a way packet that's been put into the continuing is propagating in this field okay it's not a macroscopic it's. 232 00:37:44.310 --> 00:37:45.840 Mark Kushner: A single atom dispersion. 233 00:37:47.070 --> 00:37:50.250 Mark Kushner: Okay, let me launch another bundle of electronics. 234 00:37:51.420 --> 00:37:56.700 Mark Kushner: Okay now what you see, they prop they deviated further and returned later. 235 00:37:57.660 --> 00:38:07.290 Mark Kushner: Okay, and when I calculate their return energy you notice, they have similar return energies to the ones that happened earlier but opposite ends in slope. 236 00:38:08.220 --> 00:38:29.580 Mark Kushner: OK, so the trip is anomalous here, so you might think if i'm trying to use this way packet say to make the second pulses have an some medium that's giving you opposite side chirp is not a good way to build any light source right you want at least one sign of the dispersion to control. 237 00:38:30.780 --> 00:38:31.710 Mark Kushner: And then. 238 00:38:33.030 --> 00:38:42.360 Mark Kushner: I just put the classical calculation on there, and if you if you do this again, you find that the maximum return any cheese 3.17 up. 239 00:38:45.300 --> 00:38:51.240 Mark Kushner: So let me connect this to the earth, the picture we started with this was that quantum calculation. 240 00:38:52.350 --> 00:39:04.440 Mark Kushner: And just to make the connection here is that that quantum calculation is telling me now I can characterize the dynamics of the system by considering two types of trajectories. 241 00:39:04.950 --> 00:39:10.800 Mark Kushner: One that give rise to a positive dispersion which propagates for shorter time which. 242 00:39:11.490 --> 00:39:20.190 Mark Kushner: We call the short trajectory and those that propagate for a long time and have a negative dispersion and those are the long trajectories okay. 243 00:39:20.700 --> 00:39:31.980 Mark Kushner: And so, by controlling just those two classes of checklists instead of thinking about all this kind of quantum interference of quantum pairs I may be able to gain control of the system. 244 00:39:36.390 --> 00:39:38.910 Mark Kushner: Okay, so let's look at some measurements of this. 245 00:39:40.500 --> 00:39:47.760 Mark Kushner: So the first thing I want to show you is both elastic and elastic scattering and show you the effect of the wavelength of. 246 00:39:48.630 --> 00:39:56.880 Mark Kushner: You know, producing higher energy electrons and drive in many electron many electrons or of the atom and then. 247 00:39:57.870 --> 00:40:08.760 Mark Kushner: we'll look at the case of a meeting hi monique radiation, that is when the way packet recombined back to its ground stating this rise of copyright radiation and we'll look at that scaling. 248 00:40:10.710 --> 00:40:15.060 Mark Kushner: Okay, so this is photo electron spectrum, so we put an atom in a vacuum chamber. 249 00:40:16.500 --> 00:40:28.440 Mark Kushner: We idolize the atom and then we measure the time it takes an electron they get out of the texture and calculate the energy of those electrons and so you see energy. 250 00:40:29.610 --> 00:40:35.520 Mark Kushner: versus electronic counts, we we do this experiment over at the same intensity. 251 00:40:36.780 --> 00:40:41.430 Mark Kushner: From titanium sapphire outperform microns this is. 252 00:40:43.440 --> 00:40:50.760 Mark Kushner: Yes, xenon Adam the intensity it's helped fix here the best you know we can determine that intensity. 253 00:40:51.960 --> 00:41:03.120 Mark Kushner: And what you notice is that the black line here is 800 nanometers so you could see the highest energy electrons there are about 100 volts or so. 254 00:41:04.290 --> 00:41:08.790 Mark Kushner: And by going out the four microns you can see i'm i'm seeing electrons. 255 00:41:10.200 --> 00:41:11.070 Mark Kushner: At a kilovolt. 256 00:41:12.420 --> 00:41:23.280 Mark Kushner: So again, the intensity is help fix I just turned the wavelength too long the wavelength, and my electrons gaining more and more elledge. 257 00:41:24.150 --> 00:41:33.570 Mark Kushner: Okay, and if you analyze that you're going to find that it's a Lambda squared scaling of that energy, just like you would have expected from the pond the motive. 258 00:41:34.590 --> 00:41:49.560 Mark Kushner: Now the panel on the right is a kill this view of the same experiment, so now what i'm doing is taking the spectrum, you see, on the left, remember what I told you earlier victim found the mode of units. 259 00:41:50.880 --> 00:42:02.850 Mark Kushner: And what i'm doing is plot in the energy so for each wavelength, the intensity is help fix the only way the Panda more vanities change in his point Lambda Square. 260 00:42:03.690 --> 00:42:18.420 Mark Kushner: And now i'm normalizing the absolute energy in terms of that Panda mode eventually and that's what you see plotted on on the right and what you notice that the distribution here for titanium sapphire I see I was playing laser pointer. 261 00:42:26.970 --> 00:42:28.830 Mark Kushner: That the titanium sapphire. 262 00:42:31.080 --> 00:42:39.390 Mark Kushner: produce a follow electron spectrum certainly makes energetic photons in the scale means the shape of it is a little curious. 263 00:42:40.530 --> 00:42:44.970 Mark Kushner: And you can see the classical metrics they stand up. 264 00:42:46.230 --> 00:42:51.300 Mark Kushner: And there's the limit as though there was no interaction with the call. 265 00:42:52.140 --> 00:42:56.520 Mark Kushner: Okay, so this is we refer to in the field is the simple male model. 266 00:42:56.880 --> 00:43:11.070 Mark Kushner: Just the electron put in the continuum quivers and drips and we calculate the drift energy and don't allow any and that number turns out the limit seems to be is twice the amount of energy, so there are two classical signatures. 267 00:43:12.120 --> 00:43:17.160 Mark Kushner: And you see nothing particular seems to be happening in the 800 nanometers. 268 00:43:19.170 --> 00:43:31.590 Mark Kushner: But as you move to longer and longer wavelength now you see that the electron distribution is taken on these classical signatures there's a rapid drop and a change in slope at this. 269 00:43:33.120 --> 00:43:54.900 Mark Kushner: To up point and then there's a plateau that extends out to the 10 up point okay now you notice that the demand dynamic range here is is quite large right, the number of electrons out here, those that I say must have reached scattered coaster beyond to up there's that many of them. 270 00:43:58.890 --> 00:44:10.440 Mark Kushner: Okay, one other, so this is more the kill this few you're watching how the xenon Adam is evolving from gamma greater than one the gamma less than one that is. 271 00:44:10.950 --> 00:44:20.880 Mark Kushner: As it's transitioning from a dynamics that are more multi photon him in nature to things that are more totally nine ization in nature. 272 00:44:22.260 --> 00:44:24.390 Mark Kushner: Now let me show you this. 273 00:44:26.010 --> 00:44:30.390 Mark Kushner: i'd like this plot very much so, then this is going on. 274 00:44:31.530 --> 00:44:33.630 Mark Kushner: And what we're doing is very in the wavelength. 275 00:44:34.710 --> 00:44:35.820 Mark Kushner: and intensity. 276 00:44:37.050 --> 00:44:39.300 Mark Kushner: Such that gamma is constant. 277 00:44:40.500 --> 00:44:47.400 Mark Kushner: Okay, the IP is fixed because it's the same manner, the only thing we're doing this is changing the. 278 00:44:49.170 --> 00:45:00.150 Mark Kushner: The wavelength and intensity such to keep a constant gamma so in kill dishes language, the ionization dynamics must be invariant for the same gamma. 279 00:45:00.840 --> 00:45:12.120 Mark Kushner: And you look at those spectrum, and you can see they're identical, even though I changed the wavelength around the the intensity I basically get the same ionization dynamics out of the system. 280 00:45:19.230 --> 00:45:29.820 Mark Kushner: Okay, one last example is the inelastic part like this, this is a little bit busy of a plot, but let me try to explain what's happening here. 281 00:45:31.050 --> 00:45:32.760 Mark Kushner: So this is it on again. 282 00:45:33.810 --> 00:45:40.440 Mark Kushner: exposed to for micron pulse, and what we're doing is just count benzene on our island okay. 283 00:45:41.670 --> 00:46:05.100 Mark Kushner: And what you see is the symbols are measured values and the solid curves are calculated values, so this is this curve here is the non ionizing the form xenon plus and we're kelton seen on pluses okay as a function of intensity so as the intensity increases the rate of ionization increase. 284 00:46:06.150 --> 00:46:12.990 Mark Kushner: The red solid curve is a calculation, based on a totally model. 285 00:46:14.070 --> 00:46:19.530 Mark Kushner: That we call the DK which is as more of the learning grammar of. 286 00:46:20.520 --> 00:46:35.160 Mark Kushner: The model, and you can see it faithfully reproduces the experiment, so that xenon Adam APP for my clients I would conclude from this, since this totally model works is that it's tunneling into the continuum over that whole. 287 00:46:36.030 --> 00:46:45.870 Mark Kushner: intensity rage now I can calculate if I form xenon plus I should be able to strip off the next electron the form xenon two plus. 288 00:46:46.680 --> 00:46:58.470 Mark Kushner: Okay, I can feed that into my ad K model calculate that and that gives rise to this what color is that curve blue dark blue curve. 289 00:46:59.160 --> 00:47:10.110 Mark Kushner: Okay, and you notice that the data isn't all over the place, with respect to it, in fact, if you look at that data you notice that i'm seeing xenon two plus four. 290 00:47:11.220 --> 00:47:24.750 Mark Kushner: at lower intensities then a DK to this effect i'm even see xenon three plus i'm teasing on four plus seen on five plus so what's happening is below this intensity for. 291 00:47:25.170 --> 00:47:36.480 Mark Kushner: sequential ionization of the atom in its ions we're actually not been off many more electrons and that's happening through the serie scattering process. 292 00:47:36.960 --> 00:47:49.170 Mark Kushner: Again, where the electron is driven by the field and brought back with sufficient found the mode of energy, the knockoff additional electrons so in this experiment. 293 00:47:51.030 --> 00:48:08.700 Mark Kushner: In this experiment, the amount of return energy at this wavelength in intensity it's done it's about 300 volts of return energy Okay, the old Shell of xenon is found by 244 newbie. 294 00:48:09.690 --> 00:48:23.460 Mark Kushner: So what's happening here is the one electron comes back and it's not going off to it has some probability of not going to have three, four and five all sub cycle. 295 00:48:25.650 --> 00:48:31.650 Mark Kushner: So again, you can see, the effect of the cell wavelengths. 296 00:48:33.180 --> 00:48:34.980 Mark Kushner: Right let's look at the photons. 297 00:48:36.450 --> 00:48:36.990 Mark Kushner: and 298 00:48:39.060 --> 00:48:52.560 Mark Kushner: Okay here's the process of a modern generation that i've been mentioning so you just shine this slide into a gas jet had sufficiently high density say a tour or so. 299 00:48:53.160 --> 00:49:09.030 Mark Kushner: Okay, and then you analyze the light coming out and you discover this comb of radiation, so this is an experiment, one of the early experiments done by an Louis age group at that time she was at segue. 300 00:49:10.050 --> 00:49:21.780 Mark Kushner: And what you see is she has helium Adams here exposed in this case to a titanium sapphire laser and she's seen this comb of odd harmonics coming off the album. 301 00:49:22.380 --> 00:49:32.700 Mark Kushner: And you can see the order of the harmonics 51st among all the way out to the 79 tomorrow Okay, and then this this draft right. 302 00:49:33.330 --> 00:49:59.280 Mark Kushner: And so now you guys know why it's dropping because in the semi classical model that is the three up point the electron cannot gain any more energy classically than 3.17 up and so harmonics you know being reduced in amplitude okay so that's the process of harmonic generation. 303 00:50:01.980 --> 00:50:13.440 Mark Kushner: it's a coherent calm as a how demonstrate you there a mix of of the fundamental field Okay, so when and in this experiment this right she had an 800 nanometer laser. 304 00:50:14.670 --> 00:50:23.910 Mark Kushner: And she's making 10 nanometer photons okay so which is pretty amazing, and you know again for extreme nonlinear optics. 305 00:50:26.430 --> 00:50:30.690 Mark Kushner: Okay, so here's the experiment, we did this is all gone. 306 00:50:31.920 --> 00:50:34.530 Mark Kushner: These are harmonics measured on a spectrograph. 307 00:50:36.120 --> 00:50:41.970 Mark Kushner: that's actually not true, we don't use spectrograph we actually using following the session but it doesn't matter. 308 00:50:43.080 --> 00:50:54.870 Mark Kushner: And a three wavelengths titanium sapphire 1.3 and three microns and again the intensity itself fixing the experiment and you can see, the green spectrum. 309 00:50:55.530 --> 00:51:05.760 Mark Kushner: At sapphire is producing full time somewhere around 50 volts is the cutoff Okay, and as they move to the long wavelength out the two microns. 310 00:51:07.350 --> 00:51:13.470 Mark Kushner: i'm producing full time South the 200 ev OK so again it's a simple Lambda squared argument. 311 00:51:15.630 --> 00:51:19.230 Mark Kushner: Now you notice that the amplitude is decreasing. 312 00:51:20.610 --> 00:51:30.750 Mark Kushner: And that's one of the weaknesses of going to longer wavelength, is that you dilute the way packet is propagating. 313 00:51:31.890 --> 00:51:40.500 Mark Kushner: The way packet is propagating for time proportional to the wavelength, the longer time it's fencing to continue the more it spreads. 314 00:51:41.310 --> 00:51:48.060 Mark Kushner: Okay, if it's going to recombine to its ground state the ground state is only a half an ounce true. 315 00:51:48.810 --> 00:51:54.960 Mark Kushner: If the way packet is enormous only a small amount that that the amplitude is going to recombine so. 316 00:51:55.830 --> 00:52:15.690 Mark Kushner: You know, there are tricks us in phase matching that was demonstrated by remaining Captain that can overcome this loss due to this response but there's no question, this is how you produce high energy particles in fact here is an experiment for money captain and boo to score in Vienna. 317 00:52:16.800 --> 00:52:22.110 Mark Kushner: Using a 3.9 micron laser that they had their tribe and harmonics. 318 00:52:23.580 --> 00:52:37.350 Mark Kushner: And you see that they report, in the case of helium seen photons harmonics beyond one kilovolt okay just using this simple web lay wavelengths feeling. 319 00:52:37.800 --> 00:52:45.540 Mark Kushner: So yeah that's a different wavelengths just like I showed you and our experiments, but they were able to push out into the scalable range. 320 00:52:51.990 --> 00:53:00.810 Mark Kushner: Okay, what i'll do is i'm going to skip the second part, so I can talk a little bit about the high frequency and what might be happening there. 321 00:53:02.940 --> 00:53:08.190 Mark Kushner: But as I, as I said to you the benefits of the wavelength is also. 322 00:53:10.080 --> 00:53:22.890 Mark Kushner: Part of generate ensure that at the second post Okay, because of this dispersion that we were looking at this dispersion on the single atom is improving as one goes a long way. 323 00:53:24.480 --> 00:53:26.820 Mark Kushner: Okay, but how about what high frequencies. 324 00:53:29.820 --> 00:53:41.940 Mark Kushner: Well, if you're lazy person, you know we don't have high frequency laces outside of perhaps xml laces Okay, the way we get to high frequency typically is through. 325 00:53:42.750 --> 00:53:51.330 Mark Kushner: nonlinear optics similarly that's how we would get in originally out to do, longer wavelength is by nonlinear graphics now. 326 00:53:52.110 --> 00:54:07.140 Mark Kushner: We have wonderful lasers like being developed here that will get out there, but after you know we were always forced to use a parametric processes same thing true if you want it to go into the vacuum into the actual lead so so of X Ray machine. 327 00:54:08.700 --> 00:54:29.310 Mark Kushner: But that changed in 2009 by with the demonstration of the first X Ray free electrons okay so many of you familiar with this lc Ls OK, so the CLS is makes use of this three kilometer long electronic accelerator at slack. 328 00:54:30.780 --> 00:54:43.770 Mark Kushner: It gets these free electrons that relativistic electrons and injected into a magnetic structure that has an oscillating magnetic structure the electrons the relativistic electrons. 329 00:54:44.550 --> 00:54:58.410 Mark Kushner: move down this regular they see the magnetic field and the Lorenz for spring some wiggle and if they're willing they're accelerating if they accelerate they can emit radiation Okay, the kicker is. 330 00:54:59.550 --> 00:55:08.100 Mark Kushner: If they're wiggling in their relativistic even though they're wiggling with a period, say, have a centimeter they think that wiggling had. 331 00:55:09.570 --> 00:55:25.440 Mark Kushner: A period that's boosted by the Lorenz fact the square so you go from a centimeter to an engstrom and they start a meeting and from radiation, if you do this properly, it will actually lays okay. 332 00:55:26.640 --> 00:55:37.500 Mark Kushner: it's spontaneous amplification but it's still ladies and the radiation is transverse Lee coherent larger to Lee it's. 333 00:55:38.700 --> 00:55:52.290 Mark Kushner: Not necessarily the best coherence, but it's still called here has some coherence time so so so this thing turned on in 2009 nine immediately worked okay work from. 334 00:55:54.390 --> 00:56:00.750 Mark Kushner: 250 volts out to to kill the beyond two kilobits. 335 00:56:01.950 --> 00:56:06.300 Mark Kushner: And, and let me show you what's extraordinary about it okay. 336 00:56:07.470 --> 00:56:23.850 Mark Kushner: Before I got involved with the CLS if you would have asked me 10 years earlier about seeing numbers like this, I would have thought you're dreaming, but this is the initial specifications of the hour CLS when it turned on. 337 00:56:25.200 --> 00:56:28.770 Mark Kushner: Producers Milli Joel proposed of X rays, I mean. 338 00:56:30.330 --> 00:56:42.240 Mark Kushner: You only say pulse energy when you're talking about a laser not about an x Ray so I mean I never heard anyone tell me how many millennials were coming off their synchrotron okay. 339 00:56:42.840 --> 00:56:59.070 Mark Kushner: So this was really an extraordinary device the other extraordinary number was the pulse duration, it was specter worked in the financial sector machine it immediately work that like 200 femto effects, some of our early experiments, we already down to. 340 00:57:00.450 --> 00:57:17.010 Mark Kushner: 25th of seconds or so, in fact, you know we didn't have the measure these X rays, right now, I come from the field where I do at the second so at least I had I could translate some of my metrology aren't as the hell CLS okay. 341 00:57:18.300 --> 00:57:19.620 Mark Kushner: So it's a strong field. 342 00:57:21.030 --> 00:57:27.840 Mark Kushner: Okay it's full it has transverse coherence, so I can focus this thing down to the fraction limited spot. 343 00:57:29.340 --> 00:57:31.260 Mark Kushner: And it has short pulses okay. 344 00:57:32.400 --> 00:57:40.050 Mark Kushner: So you know sounds perfect for doing strong field physics so i've been you know started to think about this. 345 00:57:41.970 --> 00:57:48.000 Mark Kushner: And let me then point out the difference between the X rays, and the. 346 00:57:49.560 --> 00:57:59.100 Mark Kushner: And the optical So when I come in with my strong field in the optical regime, I come in, I mainly interact with the Valence electrons right. 347 00:57:59.730 --> 00:58:09.990 Mark Kushner: And I can interact with those Valence electrons in a linear nonlinear way we were interested in nonlinear and, if you look at the photo cross section, then. 348 00:58:11.040 --> 00:58:16.500 Mark Kushner: The photo ionization cross section is large for these lower frequencies. 349 00:58:19.530 --> 00:58:22.800 Mark Kushner: But as I go to high frequency the. 350 00:58:24.390 --> 00:58:35.730 Mark Kushner: Valence electrons become transparent to the X rays, and now what starts happening is the initial electrons start absorbing that radiation. 351 00:58:36.900 --> 00:58:37.440 Mark Kushner: OK. 352 00:58:38.550 --> 00:58:45.390 Mark Kushner: And now the processes look different because these processes are inherently spontaneous. 353 00:58:46.590 --> 00:58:54.720 Mark Kushner: So I come in, in this case, and this is one of the first experiments, we did for the line is neon. 354 00:58:56.040 --> 00:59:11.730 Mark Kushner: With photons that above the case Shell, that is organizing the one X squared the neon that's around 850 volts okay I nice it and I leave a hole in the eggshell okay. 355 00:59:12.750 --> 00:59:24.030 Mark Kushner: That that's an excited state of the system and it wants to relax well typically in Adams, the way would relax in the optical regime, it would emit a photon. 356 00:59:24.690 --> 00:59:38.400 Mark Kushner: The photon would fill the hole in this case the o'shea process actually wins out over the admission process and electron falls in the field, the hole in the conserve energy. 357 00:59:39.810 --> 00:59:59.370 Mark Kushner: It has to kick out another electron so every phone line is event on the CLS is a tool electron process you photo Ionized speaker prompt photon and then you have no shade decay that gives rise to the screen energy electron. 358 01:00:00.450 --> 01:00:04.890 Mark Kushner: Okay, so that's a big difference in how things are done. 359 01:00:07.170 --> 01:00:12.300 Mark Kushner: So, as I said that he is neon the carriage our first experiments fault focused on me on. 360 01:00:13.980 --> 01:00:15.600 Mark Kushner: 870 votes. 361 01:00:17.400 --> 01:00:20.370 Mark Kushner: The OJ clock, you can see, is. 362 01:00:21.630 --> 01:00:23.370 Mark Kushner: 2.4 seconds. 363 01:00:25.560 --> 01:00:28.500 Mark Kushner: So the system update the case, excuse me. 364 01:00:30.840 --> 01:00:31.230 Thanks. 365 01:00:44.670 --> 01:00:49.530 Mark Kushner: The system, the case in 2.4 femtoseconds Okay, so you need these fast. 366 01:00:52.020 --> 01:00:52.200 The. 367 01:00:53.370 --> 01:00:54.960 Mark Kushner: X rays, in order to resolve that. 368 01:00:56.730 --> 01:01:02.820 Mark Kushner: Okay here here's the first experiment that i'm not going to explain it but we're just Ionized a neon. 369 01:01:04.080 --> 01:01:06.180 Mark Kushner: With this X Ray pulse. 370 01:01:07.650 --> 01:01:17.400 Mark Kushner: The only thing I want you to notice here is when we're at to kill volts were essentially stripping the entire Shell off. 371 01:01:19.320 --> 01:01:22.920 Mark Kushner: The the all the electrons off the neon the talent them. 372 01:01:25.920 --> 01:01:27.450 Mark Kushner: they're stressing part. 373 01:01:31.260 --> 01:01:46.080 Mark Kushner: Is that this experiment, when you calibrate the intensity is tented the 17 Watts per centimeter square that the focus, but yet the theory which is showing on the right, the theory users perturbation theory. 374 01:01:47.430 --> 01:01:55.860 Mark Kushner: And so, even though from my cool on gage this would seem like an enormous field, from the perspective of. 375 01:01:57.720 --> 01:02:05.220 Mark Kushner: The actual finalization it's all perturbation theory even attended the 71% in the square. 376 01:02:07.440 --> 01:02:09.600 Mark Kushner: So you know some of this makes sense. 377 01:02:12.060 --> 01:02:16.530 Mark Kushner: Since there's this Lambda squared to the pond amount of energy, the quiver. 378 01:02:17.940 --> 01:02:22.170 Mark Kushner: and bad very short wavelengths the electron doesn't quiver at all. 379 01:02:23.340 --> 01:02:23.670 Mark Kushner: Right. 380 01:02:24.690 --> 01:02:28.950 Mark Kushner: So let's go back to the Z parameter isn't allowed kinda in here. 381 01:02:30.240 --> 01:02:33.930 Mark Kushner: So here's what we do in the optical regime, this is what we looked at earlier. 382 01:02:34.950 --> 01:02:38.280 Mark Kushner: We know that as we increase the intensity or change the wavelength. 383 01:02:39.540 --> 01:02:53.100 Mark Kushner: The first thing that happens is we start that continual due to the scribble motion and then, if we have sufficient intensity along enough wavelengths the system starts ton of wine is in him with the store and the brown state. 384 01:02:56.700 --> 01:03:02.250 Mark Kushner: And this happens and intensity stuff like 10 to the 20 Watts per centimeter square or so. 385 01:03:05.130 --> 01:03:17.790 Mark Kushner: The X rays, though there's a reversing trend, so what i'm plotting here is i'm assuming it's not going to be the Valence that idolizes but the core so here I think in this calculation. 386 01:03:20.010 --> 01:03:24.090 Mark Kushner: I forgot what the core bind the damages that I think it might have been just the. 387 01:03:25.260 --> 01:03:38.280 Mark Kushner: The neon binding energy somewhere around 150 volts and I now calculate the Z and Z and Z parameters and what you can see here, as I go the higher frequency. 388 01:03:39.060 --> 01:03:50.430 Mark Kushner: Actually, the red line goes above that's the continuum distortion I shouldn't be surprised by that, because the frequency so high, the electron is not quivering in that field. 389 01:03:51.720 --> 01:04:01.080 Mark Kushner: Okay, but the blue line is the ground state distortion, which actually kicks in before the continuance thoughts. 390 01:04:03.720 --> 01:04:18.720 Mark Kushner: So the question is, you know llc LSD experiments I show you is operating here in the red point okay i'm still a few orders of magnitude off to the strong field regime, but is this picture realistic at all. 391 01:04:20.430 --> 01:04:26.100 Mark Kushner: And my feeling is it's not because as john said, this is a one electron pitch. 392 01:04:27.210 --> 01:04:27.750 Mark Kushner: and 393 01:04:29.010 --> 01:04:47.100 Mark Kushner: The assumption that when you're doing spectroscopy the X Ray regime of the Valence electrons being transparent, because the frequency is a high is in fact probably going to break down and what the X rays, perhaps could do. 394 01:04:48.480 --> 01:05:00.810 Mark Kushner: Is lead the copier in motion of these electrons in the system, which would be very different than what we see in the optical rishi now that's easy enough for me the same. 395 01:05:01.920 --> 01:05:07.440 Mark Kushner: it's probably nearly impossible for any theorists to calculate maybe what that might look like. 396 01:05:08.670 --> 01:05:12.150 Mark Kushner: And it beckons maybe for some experiments being done. 397 01:05:13.440 --> 01:05:16.710 Mark Kushner: But the X Ray pulsars as as. 398 01:05:18.060 --> 01:05:19.800 Mark Kushner: Extraordinary as they are. 399 01:05:21.030 --> 01:05:37.860 Mark Kushner: As a topic physicists I think about short pulses, not in time, but in number of cycles of the electromagnetic field okay i'll post this in the femtoseconds could be like two cycles of the electromagnetic field, this is key for drunk driving. 400 01:05:39.090 --> 01:05:44.370 Mark Kushner: Strong field effects these pulses, even though there are femtosecond. 401 01:05:45.510 --> 01:05:46.320 Mark Kushner: are still. 402 01:05:47.340 --> 01:05:56.280 Mark Kushner: 10s or hundreds cycle, so the field, so I think in order the sample destroyed field machine out of these extra resources. 403 01:05:57.660 --> 01:06:04.260 Mark Kushner: You need to compress these pulses down even further than the femtosecond now, there has been an exciting development. 404 01:06:04.770 --> 01:06:21.270 Mark Kushner: We they have been able to generate at the second pulses how the vlc Ls in fact that i've done experiments now in this mode of operation for about a half a femtosecond law they they were about anywhere in the soft X rayed to defend the X Ray regime. 405 01:06:22.410 --> 01:06:27.390 Mark Kushner: But they still want the still many, many cycles so i'm going to end here. 406 01:06:30.600 --> 01:06:40.500 Mark Kushner: And let me just I can't go by my time here because it dropped out just wanted to tell you guys just quickly that. 407 01:06:42.840 --> 01:06:48.870 Mark Kushner: During the last couple of years, when the nsf had this mid-scale initiative. 408 01:06:50.010 --> 01:06:53.550 Mark Kushner: To build the facilities throughout the United States for users. 409 01:06:54.630 --> 01:06:56.160 Mark Kushner: Michigan receive the. 410 01:06:57.390 --> 01:07:04.800 Mark Kushner: grant to build the zoom's later facility, the study identity interactions and Ohio State University. 411 01:07:06.120 --> 01:07:13.350 Mark Kushner: We received the similar grant to build an APP the second facility, and this is just the kind of. 412 01:07:14.280 --> 01:07:31.230 Mark Kushner: You know kind of CAD drawing of what that facilities is going to look like, but it's going to have the capability to generate at the second pulses to fit those can actually repulses the do all sorts of science from chemical sciences to material science. 413 01:07:32.430 --> 01:07:44.940 Mark Kushner: The key to this facility that's different than my laboratory is that the heart of this facility is based on a high repetition rate laser that can generate a kilowatt. 414 01:07:45.630 --> 01:07:58.620 Mark Kushner: of power and do that anywhere from 100 kilohertz up the two megahertz so this will hopefully open more opportunity for science for people to come and use such a specialized. 415 01:08:00.630 --> 01:08:11.730 Mark Kushner: So with that I like the end you know the work I showed you today was been the efforts and many people I just give you a snapshot of the name of the people i'm currently in my group and. 416 01:08:13.230 --> 01:08:24.330 Mark Kushner: an advertisement there that you know, there could be there are openings associated with this at the second facility that we're building in Ohio state's and thank you for your attention. 417 01:08:38.640 --> 01:08:39.840 Mark Kushner: Are there any questions. 418 01:08:44.310 --> 01:08:49.620 Mark Kushner: The philosophy behind this is the idea that the idea is for. 419 01:08:51.780 --> 01:08:55.260 Mark Kushner: revisions visitors to our generation my translates to. 420 01:09:00.390 --> 01:09:01.530 Mark Kushner: ya know. 421 01:09:02.730 --> 01:09:12.600 Mark Kushner: My feeling is that physics, will not be relevant, because the key to that physics to three step or the risk scattering is the ability to quiver the electrons. 422 01:09:13.830 --> 01:09:15.720 Mark Kushner: And the electrons are not gonna quiver. 423 01:09:17.130 --> 01:09:19.290 Mark Kushner: Or if you can get them the quiver. 424 01:09:21.600 --> 01:09:31.680 Mark Kushner: there's a secondary effect that was looked up in theory in the 90s, is that if you can quiver those electrons with large enough displacement. 425 01:09:34.110 --> 01:09:35.820 Mark Kushner: The frequency is so high. 426 01:09:37.050 --> 01:09:46.680 Mark Kushner: That the electrons spends most of its time at the outer turning points of its trajectory in no time at the nucleus and. 427 01:09:47.550 --> 01:10:04.500 Mark Kushner: The more you try to organize it the worse it gets you just keep pulling the wave function away from the nucleus, and the thing won't Ionized, this was an effect called aerobatic stabilization, so no, I think the physics, will be very different. 428 01:10:06.570 --> 01:10:18.870 Mark Kushner: frequencies, I mean some people down that it exists, I don't understand why it wouldn't exist, you just got to find the word right circumstances in order to exploit this. 429 01:10:24.090 --> 01:10:29.670 Mark Kushner: Is all said they were also using us. 430 01:10:35.940 --> 01:10:42.360 Mark Kushner: No, no, no, was it it's i'm actually putting in an energy modulation. 431 01:10:44.190 --> 01:10:47.010 Mark Kushner: Controlled energy modulation on the electron beam. 432 01:10:48.600 --> 01:11:06.120 Mark Kushner: So they get a pre bunching and they and they can do this in such a way that those bunches Okay, they go through skein which, as you know, is similar to stretch or compressor and now language and they're able to get these very short burst. 433 01:11:07.200 --> 01:11:08.160 Mark Kushner: That or. 434 01:11:09.480 --> 01:11:14.970 Mark Kushner: very short bursts of electrons that will lays over a very short period of time. 435 01:11:16.770 --> 01:11:18.690 Mark Kushner: So, knowing it's it's not. 436 01:11:19.920 --> 01:11:33.570 Mark Kushner: You know kind of it's not this idea that be used in the nittany this what they call high gain high harmonic generation, where they generate harmonics or have some seed field. 437 01:11:34.170 --> 01:11:46.350 Mark Kushner: To make higher frequencies and short incoherent pulses, this is all done with the accelerator yeah and and you know they use what they call a module eight a section in an amplifier. 438 01:11:49.050 --> 01:11:57.060 Mark Kushner: And it works very well, I mean we've now used it in a couple of runs and as long as the machine is working well. 439 01:11:58.020 --> 01:12:04.650 Mark Kushner: We are getting short pulses, you know there's all the problems like associated with doing an experiment on the next fell. 440 01:12:05.040 --> 01:12:17.880 Mark Kushner: If your timing it against some of the source, like when normally are they do metrology like laser there's no synchronization so you got to do a post analysis and we have tricks, now that we can tag things. 441 01:12:21.120 --> 01:12:22.590 Mark Kushner: So kilowatts laser. 442 01:12:24.510 --> 01:12:29.280 Mark Kushner: Vision rate low energy, what does that bring different to the physics physics, or with others. 443 01:12:31.050 --> 01:12:36.720 Mark Kushner: yeah yeah that's a good question um Okay, let me give you an example. 444 01:12:38.910 --> 01:12:46.770 Mark Kushner: One of the stations are going to be built, based on our past right and our purpose is to study band structure and. 445 01:12:48.330 --> 01:12:53.670 Mark Kushner: One might want to study dynamics of band structure. 446 01:12:54.990 --> 01:13:14.160 Mark Kushner: Well, an opposite experiment is done by you know hitting the surface, with some ionizing radiation Okay, but you do that gently right you only create one electron at a time, because if you create more than there you distort the band structure. 447 01:13:16.320 --> 01:13:26.730 Mark Kushner: So that's an experiment that doesn't call for a lot of photons a lot of photons is not a good thing What it needs is duty cycle. 448 01:13:28.200 --> 01:13:36.000 Mark Kushner: And so what do we bring differently than, say doing office on a synchrotron know we have femtosecond pulses. 449 01:13:37.020 --> 01:13:43.770 Mark Kushner: So you can do time resolved artists on our facility at mega hertz repetition rates. 450 01:13:45.570 --> 01:13:49.290 Mark Kushner: And I think that that becomes a you know, a kind of real breakthrough. 451 01:13:51.540 --> 01:13:57.780 Mark Kushner: So the other experiments that were thinking about what one of the inspirations is based on stm. 452 01:13:59.550 --> 01:14:02.820 Mark Kushner: scan telling telling Mike mark I cross. 453 01:14:04.020 --> 01:14:31.230 Mark Kushner: And the idea is to use the X rays, this has been demonstrated on synchrotron to get elemental contrast in you know your stm microscope so you excite around the edge of the particular material and you get elemental and now we'll also attempt, for the first time the game temporal. 454 01:14:33.960 --> 01:14:34.500 Just because. 455 01:14:36.000 --> 01:14:40.530 Mark Kushner: The high REP well the high repetition rate the high frequency. 456 01:14:42.510 --> 01:14:50.940 Mark Kushner: Of the you need X Ray or you need at least X UV radiation to do these experiments was sort of tax rates but yeah the high. 457 01:14:52.170 --> 01:14:57.540 Mark Kushner: The high REP rate becomes the enabling technology to open applications. 458 01:15:03.210 --> 01:15:04.560 Any more questions. 459 01:15:06.990 --> 01:15:07.440 Mark Kushner: No. 460 01:15:14.310 --> 01:15:19.950 Mark Kushner: Thank you, thank you and hope to see you all next week next seminar.