 So, as we begin already, it is my pleasure to introduce you to the expert with the Spark and the Bayer Archive, who comes from Nijmegen University. And, as Mr. Dr. Bergmann introduced, Bars Spark is the founder of the Archive University, in which he said that he sort of pressed the project to the university at that time, two mountain safes. And then he transitioned to Berlin, to an extra-wide institute, which is a unique institute in Germany, and to a brand new institute. And he was there for, I think, from 2006 to 2006, and that was the 67 years, first as a postdoc, and then as a group leader. And then he went back to Nijmegen to take over, first as a position, as a senior track position, and maybe as some interest to the young people. Only three years later, he was a school professor, I think it's nice. And I can talk a long time about all his scientific acknowledgment to see this project as a brand, and not to mention it. His favorite, in terms of hypothesis, is Nijmegen, in terms of journals and science. That's all nice, but what I really want to say is that I think he's a fantastic scientist, and hopefully this will show at today's talk. I don't know if this is what he's talking about. But anyway, and while we're in Europe, I know we've seen that in 2003, 2004, and we always have content design tips in this project. And that's really what it's all about. And then one thing which I hope it also becomes clear with strong insight. The agreement to build on new scientific instruments opens possibilities for making extraordinary science, and I think people just thought that. So with that, please pass it over here, and I hope this is not going to work. Thank you very much, Henry, for this same nice introduction, and for the invitation to come for the hours. We tell about the work we do in Nijmegen, and I apologize for the delays. Actually, filling all these laptops and connecting them to his assistants, made it actually more difficult than manipulating more tools in there. Anyway, so the work that we do in Nijmegen is really passionate about trying to understand collisions between molecules and evidence. I hope to make clear as we develop some unique technology actually to manipulate molecules in order to do this in very high level of precision. So why are we so interested in molecular collisions? Well, there are a number of reasons. The first reason is this happens all around us. If you want to understand the world around us, whether it be in atmospheric chemistry, in combustion, or even in astrochemistry, you really need to know how molecules collide with each other. Because ultimately, this will be an input in order to try to understand the macroscopic behavior of these co-existent. But there's a second reason. And that is that molecules and atoms, when they collide, it is like an ultimate pro for quantum mechanics or quantum chemistry. Because a molecule and an atom, obviously, is a quantum object. And if you study them in complete isolation from any environment, you really have a good handle of trying to test quantum mechanical methods and theories. And this is what we would like to do. So ultimately, we would like to get, as we call it, the full understanding of these quantum mechanical systems. And with a full understanding, I mean that you'd like to be able to write down the Hamiltonian for first principles, solve the equations, and accurately describe and predict the behavior of molecules when they collide. And where do we stand in this field at the moment? Well, actually, we are not that good at this. So this full understanding at the moment is really only possible for a very simplest of systems. Basically, a simple diagram of a molecule scattered with an atom. Only then can we get this complete understanding that the theory is almost exact. But if we step up the complexity better, only one step, and we place this atom for a molecule, the equations are so difficult that we cannot be solved. And so this is, of course, an issue. And also for me, this is kind of bizarre, because we're living in the year 2023. We can do crazy things in science. We can detect gravitational waves. We can make a photograph of a black hole. With a simple collision between two oxygen molecules, we cannot actually describe and predict the full first principles of all mechanics. And this actually is a situation in an out there already for a long, long, long time, basically from the start of quantum mechanics. So here you see a citation by Paul V. Hartman when he made it in 1939, where he says that the fundamental laws necessary for the mathematical treatment of a large part of physics and the whole of chemistry are thus completely known. And the difficulty lies only in the fact that application of these laws leads to equations that are far too complex to be solved. And so the problem is not that we don't understand the fundamental physics or fundamental chemistry. Everything is in principle mode. We know all the interactions, so we get right on the full Hamiltonian. Our problem is just mathematics. We don't know how to solve these equations to actually get a proper description of the system. And this is still true up to today. And so how do we make advancement in this field? Well, this is basically by a synergy between experiment and theory. So what the experimentalists try to do is build any more complex instruments in order to really look in high detail how these molecules collide with each other and what is the output of such a collision. Which then of course can be put back into the theory, so theoreticians calculate what they expect. And of course you compare with the experimental findings. And by looping this over and over again, we ever get deeper into this full understanding of the true description of these quantum systems. And here you see you only got the Nobel Prize for the development of the cross-molecular beam techniques. Instead of being a form of this universal cross-beam machine and Berkeley, I think this photo must be in the 70s or so. But really the workforce in this field is the use of molecular beams. I don't know how familiar you are with molecular beams, but basically what you do in a molecular beam is you take a container of high pressure gas in your vacuum system and you have a small leak in that container. Such that molecules can actually travel out. And because they travel into vacuum, they expand. And as they expand, they cool down over the degrees of freedom. And in this expanding jet, you can basically take the center core of this by the skimmer. You basically form this molecular beam. So this is just a stream of molecules where all these molecules more or less have the same speed. And they are internally cooled down in the Novus Foundation 106. And so this is really the workforce in many of these type of experiments. And then there's cross-beam machine. You basically take two of those molecular beams under some angle and right at the crossing point of these two molecular beams, you eat it during a collision experiment. So that's where you have collisions between molecules in complete isolation from anything else. And also the beauty of this is that molecules can only scanner a maximum one time. So you really see very individual collision processes in these conditions in high heat. So this is basically what's out there in the field already for many years. And many people have to typically do this, need to do our core acknowledge of molecular collisions. But there's a second argument. So this was important already for decades. But the last two, one or two decades or so, another argumentation, an argument game about to measure this molecular collision, that is to try to measure these collisions at very low temperatures. And this is illustrated here. So to measure these collisions or probe them at high temperatures, you basically have still a quantum object, but still you can get a far away with just Newtonian mechanics. You can see some molecules and atoms as being like billion balls that scatter on a billion table. And although of course you need quantum mechanics to get a cool answer of what you're doing, but with these mechanical laws you get a fire. But of course this is completely not true if you cool everything down to very low temperatures. So this is where quantum mechanics really starts to measure, as you all know, as the temperature drops to the value wavelength of particles between larger and larger. And at some point the wavelengths of these metal waves that we have here so large that they really start dominating anything through this collision. And so then instead of having billion balls that are colliding with each other, which is basically what you're used to, where the billion-stable light they come together and they knock into a certain direction, now you have two waves coming together. And two waves coming together and colliding, obviously leads to a fundamental different interaction, where you can interfere. And of course it's very interesting to see this interfering quantum waves during these molecular collisions that you observe there. This is much like throwing a stone in a pond. So you see ripples on the water surface by throwing this stone in. And as I've chosen this image here, because it's basically the images that they make nowadays from these colliding molecules in this very cold region, they pretty much resemble such an image from the water surface where you throw a stone in it. And from this distribution of basically these waveforms that you see here, you can directly trace back what kind of colliding chemical waves are underlying the collision. And so that will be something that I'll show you later. And so let's go a little bit more in detail. So the quest for these localization energies, what kind of things can we expect when we are there? Well, one of the things is really the emergence of new phenomena that says we do not occur at high collisions. And one of these states, I think it's fair to call this like one of the Holy Grails in this field for a number of years, is the observation of so-called scattering resonances. So here you see a prediction for these kind of scattering resonances for CO molecules called monoxide scattering with helium. And you see these type of resonances in all kind of systems. And so this is the American prediction, so it's calculated. And what you see here on the horizontal axis is the collision energy in wave numbers. Now, one wave number is about one Kelvin, so this is kind of the Kelvin scale here. And the vertical axis is the cross-section for collision to occur. So just the probability that these things are scattering in each other. And what you now see is that you go from these higher energies all the way down to lower energies at specific energies here, you see the cross-section over some of these are all tremendous. You get these spikes. This is what you call these resonances. I'll go back to this later. But these resonances they really occur because at these energies where these resonances occur, you do have individual partial waves that all of a sudden dominate the whole scattering. And so this is where you can actually start seeing the influence of this individual partial wave. And this is what people have been interested in for a long time. But it's also clear to be able to observe this experimentally because you've got to be hard because first of all you need to go very low-producing energies, which you can't do. It's not so easy to get there. But most importantly, you also need to have a very high resolution as you scan the energy in the energy regime. Now, if you under-sample these very narrow features, you easily do not observe them. So you also need very high resolution to get there. Well, once you have measured these resonances, the energy is now so-called that actually you can start tuning these resonances with external fields. The idea is that if you now apply extra electric or magnetic field to the system where the same amount of start energy can be now the same order of the collision energy. Well, that, of course, will start moving around all these resonances and start manipulating these collision concepts. So this is what people are very interested in. If you go even colder, people also vary into other things. You can, for instance, use these cold-molecules, particularly when they have a dipole mode, and you can store them in optical lettuce. And they actually use all these molecules in these lettuce points here, basically as a simulator for many body visits. So basically you have to lay it here, your own eye symbol, where you can start manipulating individual molecules at each of the deficit sites, and then look at a moment of how the system then evolves and compare it to here. People are very excited about molecules that have a dipole moment. Also, come back to that later in my work. When a dipole-dipole interaction is very long-range, so molecules start feeling each other in a very large distance, but also very highly anisotropic. So it really means what is the relative orientation of the two dipoles when they scatter. This really determines the outcome of the collision. You can start tuning your interaction from attractive to repulsive, simply by changing the value of the relative orientation of the dipole. So many people are working on that, too. And there are even some proposals for using optical polar molecules in product computation. So the idea is that you take a whole array and use these molecules, basically as a qubit, in product computation systems. So there's a lot of spheres really that you're exploding in last few years, I think, that are very interesting in this whole problem. That's great. So we are not that open-art experiments we are more in this regime where you can see the scattering lessons that are also in the data. So that's like a simple cartoon of a scattering experiment. So if you care of these molecules in a very high precision with each other, well, if you think about it, what do you need to do? Well, there are two sides of a nail here. Before the collision, of course, you need to have some control over your molecule so that you exactly know what you're sending. You'd like to be able to control the internal degrees of freedom of your molecule but also the external degrees of freedom. Basically, you'd like to be able to control the velocity, the relative orientation, and so forth. Well, then you let those molecules collide in this control permission and it brings to those molecules, they change due to the collision. They need to be able to read out, escape to the two small molecules with a certain detection. So what has now been so far basically the bottleneck in these cross-need experiments will be made a step forward. The bottleneck has not so much with on the right-hand side of the diagram, the detection. Nowadays, our really fancy laser-based detection techniques basically allows you to measure all the properties of your molecule. Even the reflection of the molecules in velocity space that are due to collision can be directly measured. And actually, the use in our experiment with a very nice technique is called velocity net-imaging. Some of you may have heard of it or have been using it in their life, I would say. For the course, here from Nijmegen and in this private held is the Nijmegen invention which was invented by Degen Faag in 1907. This really allows you to basically measure all the molecules you'd like to know. It's laser-based, so you get constant sensitivity but also you measure directly this reflection from the initial velocity data. So basically it maps all the velocities of the molecules in the two-dimensional plane. So this part of the metal is basically solved. The techniques are there can be used. The problem really is in this preparation. So these molecular beam techniques that I showed you earlier are great, they are nice, all the molecules in the beam still do different things. Some molecules go faster, some molecules go slower and a certain angle is spread so this is certainly not sufficient in order to map out these revolutions that I showed you. So here this is where we need to work on and to be able to control our molecules better. And then you look back in history and you think about what physicists have been doing over the last 100 years or so in controlling particles and this is really impressive. So physicists have learned to control particles really basically changing their temperature or energy by about 25 oz of magnitude. The highest energies can be made with charged particles and you all know of course the example of the large Hadron collider at CERN but also here you have this storage range with ions and so it's actually relatively easy to manipulate ions because you can just use particles. Then you can speed them up to the velocity closer to the speed of light. All the way on the other end of the history the coalesce template can be made with ultra cool atoms where lasers can be used to really cool down atoms to the temperature as well close to the nanoballons nowadays and this actually leads to even the formation of new states of matter like those ions that we can say. So all these kind of things have been developed through the HIPAA particles in the fourth grade but where do our molecules fit in? Our molecules are neutral but don't have a charge so in principle charged particle accelerates cannot be used for our molecules. We have the same problem with laser cooling laser cooling really only works for atoms nowadays now a few molecules have laser cooling still it's very difficult and it's not suitable for our private experiment. So basically none of these techniques can be used for the molecules and we have to be designed to join the work and design new methods from scratch. Although it can be inspired by one of these methods in particular these reunites which are chemical accelerators. And so the question you can ask yourself is can we now also control neutral molecules in systems like the linear accelerator but then of course the problem is our molecules will have charge so the too long force that we use in the reunites is zero for our molecules but there's a second order of effect if you take a molecule that doesn't have a charge with a dipole moment you can still exert a force in the molecule. So this is going to be based back to the Stern-Gerlitz term the idea is that you take a molecule that has a dipole moment and if you place that into an inhomogeneous electric field you basically see that there is a net load force pointing in this case to the left that wants to pull the molecules in towards this e-wrestle as it appears. And so there is certainly a force on a dipole molecule which can manipulate its motion. It is just that this force is very small so if you compare the forces that you have on a charge like in a linear accelerator to a charge particle you see that the force acting from a dipole moment of a molecule is about 9 volts of magnitude smaller so you can do exactly the same manipulation to neutral thermal molecules as you can do to charge particle accelerates, bunches, simple forms, storage records you can do it all you just have to go with 9 volts of magnitude smaller. Luckily it is not 9 volts of magnitude more certain. And this is what we do in this target simulator so I don't want to explain you too much about how this device really works in detail but basically it is a whole series of highly polished stainless steel electrodes that you pose to high voltage such that molecules that fly through these electrodes they always feel a force from behind and it continuously sped up or they always feel a force proposing their motion and then they continuously slow down. And so basically the take-home message from this device is that it adds a knot to your molecular beam machine that you can turn on and you can dilate any velocity that you wish ranging from very high velocities all the way down to the stainless steel. And so because this whole device works or grabs on the start effect of a moment to it, you also get a very high state of purity in these beams you get a very narrow process to have a very small angle of state. And so the combination of all these properties really makes this device an excellent starting point for collision experiments in the liquid process and also again I'm proud to say that because of the 9-vague invention we started by Pierre Abneyer in 1909 And so it's really the combination of these two techniques that make very high-resolution experiments possible. So back to our diagram of what we want to achieve in such an experiment the control model of the particle is being done by the starter accelerator and it's reading out that the collision product is being done by testing that ability. So this is the best of both worlds I've written in my house. The 9-vague invention. Anyway, so this is then our flawless look so we produce the molecular beam without starter accelerator which is then crossed here at the center point of the conventional beam of energy molecules at any angle, 9-vague, 8-vague or a small angle and then we do this loss in the net imaging. I don't want to say too much about how it works but basically you ionize your neutral molecules with lasers using ranking. So right here at the crossing point you can work your neutrals into ions and then you have a whole set of electricity lenses that accelerate those ions upwards and these lenses they are built such that basically you get a direct net here at the conventional surface by each position all this to the net represents a velocity in this plane so you directly get a net of the velocity so you're measuring the velocity so I say velocity net energy so this is how it works but this is a night animation on an experimenter I see this you would both have made so we made the comparison with the beam it's passed through the accelerator this one is 3 meters long so you have those electric field stages continue to be manipulated with velocity and then it comes out with a very well defined velocity that you have on a computer control and then it collides with a secondary beam that happens on normal fields then your ionization lasers come in you convert the ions and you map the velocity products onto this two-dimensional screen so this is how it experiments ok so what I would like to show you very brief I don't want to do much detail on all of those topics but the first is to just get you acquainted with these is the observation of total diffraction oscillations that would like to spend some time on the observation of these low energy scattering resonance that helps to introduce the way into the introduction then a very recent experiment on low energy collisions between two molecular dipoles and last but not least the construction of a Z-Mod accelerator the magnetic animal of the static accelerator which we now use for reactants and if I forget to tell you I would like to say that most of the theory of what experiments that we do is done by Gérard Houdelon Hansen-Beragel and Thijs Carmel the new higher institute also in the world ok here you see one of those velocity net images of an old radical scattering with neon atoms and so basically you have to interpret this image as the velocity axis on the right-hand axis the velocity axis here on the bottom so basically you directly get the velocity net and the incoming and old molecules so that basically represents the incoming philosophy of the molecular beam is this solid arrow here with ends up here so all the molecules that end up here basically are unscheduled so this would be the initial velocity factor of our molecules but now the molecules scatter and due to the scattering with the neon atoms they can get deflected and this deflection angle you see here basically by those dash lines so all the molecules end up somewhere in the circle it needs to be a circle in the velocity state due to the conservation of energy in angular momentum but where they end up in this space that is governed by the potential by the interaction with the scattering and so by reading out the intensity distribution along this circle you basically directly measure the differential cross-section so that's the beauty of this velocity energy but you also see that these images are still kind of blobby so they're still kind of fat and why are they so wobbly that is because these molecular beams that I mentioned before they don't have ideal velocity spreads all those molecules have a different velocity so you're scattering sometimes they're slightly faster sometimes they're slightly slower so that leads to all kinds of these kind of circles they're all molecular beams but now if you do the same experiment now you pass there no radicals you get this so you nicely clean up this whole image it becomes much more sharper in the radial direction and you start seeing now some structure you see regions of higher density lower density, higher density, lower density and so forth and so what do we see here this is just quantum diffraction of these melodies so basically you would see this or interpret this experiment as basically a quantum wave you would see this object, the medium atom and this would start diffracting pretty much like it used to when light falls on a pinhole you see diffraction pattern on the screen this is what matter waves also mean and so by improving this vessel which you do in your psycho-permanent technology you can really start observing these the original diffraction primitives and learn something about the quantum mechanical behavior underlying the scattering and this is all with high energies it was like hundreds of Kelvin and you can see this quantum mechanical behavior okay let's move on to lower energies so I talked about this before where you see scattering residence in these very low energies this is also what you expect to see where no molecules are scattering with helium atoms so I don't want to say again too much about scattering residence it is basically what it is it is that when the molecules come together at very low energy the funnel through is a typical barrier that is near in the interaction potential and the startling probability is actually high but on the other side of the barrier there happens to be a volume state so basically the anode and union we can hold in the volume state well every time that your collision energy exactly matches the energy of such a volume state that is where this residence occurs and this is exactly where one of those quantum mechanical waves really starts dominating the scattering area and this is what we would like to be able to see and so we set out to do this and around that time other people have been working on this it is a beautiful experiment in Bordeaux the residence has been measured between oxygen and H2 it is still using conventional molecular technology so you really see beautiful residence stream structures and also very nice experiment with the Weissmann Institute in Israel by Adnan Avicius and Goldworthis where they dent around a beam of melastable helium atoms with a Genshin overlap with other beams in order to really get very low velocity and see the resonance but this is all in the integral cross-section so you see now this residence is in the integral cross-section of the function energy but you don't directly observe these waves that are prominent for that experiment you can use this imaging method that I will show you in a minute so we set out to do this we took out a accelerator passed a molecular anode for it now focused into the hexapole in the reaction region the angle we come here with the beam of cryogen helium in order to make the helium slow and they scatter here at a small angle reaching energies of about 0.15 wave number but this is very low it is indeed where you start observing the scattering moment and this is then what you measure so I have to explain to you this is made especially important but the rotation of round-stake of NO is the game with one-half-stake because it actually has two components you have an upper component and a lower component we call that a lava problem it doesn't really matter what matters for the experiment is that we start the accelerator only transmitting smaller things so this is the initial state of the experiment before the collision and this lower component is basically rejected by the accelerator so all the population in that state is gone before the collision occurs that state is empty and so what now happens in the collision is due to the impact with the helium atoms those molecule that are in the f-state in the upper component they can go down and end up in the e-state which we now can state-selectively measure with our laser so we detect molecules that arrive in this e-state with only slightly the lower end of the building in the f-state so we state-selectively look at those molecules and if you do that now as a function of the NO velocity or as a function of the collision energy you see this you see these beautiful resonance structures these are actually very pronounced resonance these are exactly the same as we did with children before and actually then you go to your t-auditions and you ask them to calculate that of course they claim the molecule is an atom, you can calculate exactly so if it should be a blue state and out of t-auditions they use the best team that is out there in the case of the CCFD method of the quantum chemistry this is why we work also as a big old standard of the quantum chemistry and you get this it's a good agreement but still there is a little bit of deviation there and this is because well CCFDP actually is not sufficient to work and more if you look at molecular proteins at this resolution and so in a heroic effort they developed a new TUB based on the next level of TUB CCFDPQ but if you look at the quadruple expectations of the electron you get those resonances agreement a lot better so this is again one example of trying to cycle this it's of course a detail but still as you go down to go up in resolution you can look at those processes in more detail at some point you start finding that you also need the next level of TUB and this is how we make progress in this future but this is again in the integral cross-section I'm excited now to look at these quantum waves how do these quantum waves manifest themselves in for instance differential cross-section and this is what I illustrate here so as these quantum waves come in they scatter and you have some certain waves that go out but at these resonances only a few partial waves as we call them these are those quantum waves on the line is getting there they have a quantum number there's just orbital in these quantum states and so actually if this momentum a certain value that actually leads to kind of a different angle of distribution of the reporting products and by means of this personal imaging the hope was actually to start recording this angle of distribution that you can directly see these quantum waves at work so we can now go back to this resonance plot so again this is the integral cross-section we saw before but now all the energies that are marked on here we can now talk to our experiment and measure the angle of distribution of the products using the cross-section method and what you then see is something very striking so as you go higher energies all the way down to lower energies as we sample over these resonances well those energies are followed here the upper row is the experiment the lower one is the simulation based on this new CC energy cube theory actually you see that as you scan over these resonances this angle of distribution changes dramatically here you see only intensity at the right there's mean score what's gathered moment when you have only deflected a little bit there's not much but as you change the energy only one wave number that's from here to here there's one large back-scarrying and some side-scarrying from here and as you go down you see you get a very different pattern and so forth these different patterns can be directly traced back to this interference of these individual components and as it has been with yours so long not so many of those components there but it's interference actually when you focus quite a time and you can actually directly calculate the difference from here so this is the lowest energy here is one wave number the angle is lower so that's from the next one you see here one wave wave number all the way down from the two wave number and you see nicely how this angle of distribution also becomes easier and that's simply because the number of these quantum mechanical waves is reduced and actually in this limit of 22 wave number you only have two wave tracks yeah, yeah this is for the speciality the variable length of this here we have a rise at the region where we only have S and P wave one important moment and so this is the lowest part where we stay for chemical if you would go even lower or you enter in pure S waves that's neither the lowest energy there and we get the right pure performance so not quite there yet but we'll be closer okay so that is I think all I want to say about these resonances one of the questions I get a lot when I give presentations okay, well it was nice and I wanted for those beams nice on the control that we can celebrate but what about the other one I mean you're still scattering with this boring beam or here you have which is kind of conventional technology so isn't that limiting them the energy that you can have in resolution yeah, of course, yeah, that is true in principle you want to control both of the scattering power but as you can imagine that I think it's far from because we tried nevertheless so we set up a research program where also we replace this beam and also try to get the second beam on control not just to get low energy by resolution but in particular to measure interaction between two polar molecules because the physics of two polar molecules interacting with each other is just fundamentally different from molecules interacting with each other so we also need to try to control the dipole dipole so the idea of this experiment is actually the second to the second one to run low experiments at the same time so I know again it's passed through this one but now this helium beam is replaced by a beam called ammonia which is a conventional beam of ammonia molecule but you have to make those beams by seeing these molecules in their particular carrier gas and it's critical, you know we can make a nice beam of ammonia but then you would basically collide both with the ammonia so you need to kind of separate out these critical reactions and they do that, it's not the second spark which I already mentioned maybe the next step could be separate for now for hexapoles so basically such a hexapole is simply like a positive lens of molecule so you can focus molecules such a hexapole into a point so what we do here we have three hexapoles in succession with the beam stop here which is replaced by the beam axis and the idea is that molecules they are focused around this beam stop and ammonia molecules have the dipoles so they follow the right path critical atoms just bounce on the beam stop and that's where we get rid of them so they're focused around this beam stop into the diaphragm and they re-focus that by the second hexapole in the interaction and that's where they meet the other so this is the anti-level diagram of both molecules so we have an old repair to the lowest rotational state that it again has its lambda complex so it is actually in the red line in the top of the state of F and the ammonia is a very complicated energy level structure but also that we produce in the lowest rotational state and also that has its kind of illusion the lambda structure makes a real result of the other one so this experiment work I'll show you in a minute the results but then we go a bit greedy it's okay this hexapole actually is mounted on a 45 degrees with yellow axis of course that's limiting the temperature but now that we are able to also control the secondary beam with this hexapole why not bending one of those hexapoles into a curvature and basically do this merge scheme that also was done at the Weizmann Institute where I had my PhD and so we built this curved hexapole and it was coming from the side here and the rest of the experiment is the same so now ammonia and CO2 that doesn't really matter and this hexapole of that now into a curvature such that it basically lines up and gets used to the structure and what you are now in is two molecules basically merging with each other and if they both at the same speed basically have zero relative velocity that means there needs to be very very low kinetic energy we are after in the experiment so here you see results from the imaging so again we image here the NO radical in this experiment and basically by using these merge beams and also the straight hexapoles we could change the collision energy from the moment we reached this point over 8 wave numbers so that's about 100 village Kelvin but you could tune it all the way out to 580 wave numbers so hundreds of Kelvin 4 orders of magnitude you can now study the behavior of this collision and not surprisingly you also start finding very different mechanisms as you scan the energy over these 4 orders of magnitude and so divided up here in 3 seconds the very low energy regime the intermediate energy regime and the very high so let's now look at this very high energy machine here what you see all of a sudden is not just one ring as you have seen in the previous experiment now a whole series of concentric rings and why don't we see more than one ring in the experiment but that actually means it's playable because we are now colliding with 2 molecules and as molecules come in they collide now both can get rotationally excited in the molecule and the idea of this experiment is we only detect the NO radical in our laser so for instance we part our laser to detect a certain final state of NO which is energetically accessible at least in the high energy so we know we are detecting NO in a certain excited rotation state but we are not detecting the ammonia in this state we don't have the ammonia laser part of the experiment but ammonia in this region can get to any rotation state we can do all these kind of transitions and we don't know it but as they go to different rotation transitions there is energy available that means they have less kinetic energy after the collision to record but that is encoded in our NO philosophy spectrum which we measure with philosophy and so that is why we see all these concept of rings here the outer rings corresponds to the fastest NO that means they correlate with ammonia that state in the total rotation ground state these inner rings corresponds to NO being detected in this state so at the same time ammonia into incidence along excited or excited fibrational levels and so basically by measuring only the NO we still get a full correlated energy distribution of the molecule and by measuring this and comparing the few I learn a lot about how these two molecules excite with respect to each other and why they are among the human people then there is this intermediate energy regime where we really found some very strange behaviour of the scattering which I think I will skip if we deal with time because I would like to go with the NO energy regime which is the I think the most interesting result of this experiment so if you go to NO energy regime you see that these images now are really only one ring left and the reason is the energy has become so low there is simply not enough energy anymore for more molecules to excite to begin with just all the channels are closed and so you only see as the energy goes down you have the size of these rings but smaller and smaller but the lowest energy nothing happens so basically we are in the center of mass so arguably you could say while we are imaging at some point it loses a little bit of its beauty because there is not much to give you cannot resolve an structure and that is just true but then of course you can always still measure integral cross-section and that is what we hear also when you see the result here so as the energy goes down from this all the way down to this point you can see this cross-section really goes on two rows increases by five so just a scattering point that goes up and the reason for that is just two dipoles and it is very small interaction and it is also what we expect and so the blue curve here is the altitude of theory and so we are quite happy until you look at a little bit more detail and you see it only here in the next vlog so this is the same data that I have looked at on the log-log scale so of course our experiment ends at 48 weight almost we cannot do much better than that in theory of course we can't take anything so in theory you can just go down all the way to the altitude of the gene which is called the heat perforation and then you see something very interesting that people will realize before is that actually this cross-section this theory cross-section here has a local maximum it goes down again this is not what we expect but it goes down again before it ends and there are two limits here that the blue makes sense the very low energy regime where you have only s-phase scattering l equal to zero this is where the weak pressure of laws shoot all and the weak nerve predicts the police type of systems the cross-section to the scale the energy to the power minus one half that's it at the high energy side actually there's not a theory which for dipole scattering predicts an energy dependence e to the power minus two thirds and that's also what we find theoretically in most of the scientists so that's also pretty sure until we realize it actually doesn't make any sense because we do have two molecules in the dipole and that's why naively we'll take it but actually and this is very subtle argument but it's an important argument the molecules that we use they do not have to be in dipole and so what you should realize is that we should not observe as long as they're model at all and the reason for that is again this strange rotational structure that we have in our molecules we have this lava topic in a node and inversion topic in ammonia and other states are populated before the collision but these states have definite parity and molecules instead of their definite parity the expectation value of the dipole moment operator is zero and you can easily understand that because if you would sandwich your dipole moment operator with each of these states and minus parity, dipole moment is minus parity to minus times minus times minus interval over all states means zero so our molecules do not have a dipole moment the dipole moment is only in use when you bring this moment to an active field for instance starting to mix these two parity states and that's why we can actually manipulate them and start to accelerate it to the middle but our molecules here they scatter in zero field and so in zero field this mixing of parity states simply does not occur and so it's really weird that we see launch of that so why actually do we see that at the same time also the explanation why we see this kind of lump structure the reason is as follows if you now calculate it goes a little bit too much detail but if you calculate the interaction potential between the two particles but now as a function of the distance between the particles they just solve the Hamiltonian as a function of the distance when you get the energy out basically when you see it what is very far apart my argument isn't be true the dipole moment really is zero and so they don't see the dipole moment and they behave as if they have distance between the direction one over half of the sixth but as the molecules come closer actually by virtue of their close proximity they start formalizing each other mixing these two parity states and that's exactly what we see happening here in this buckle point the interaction energy goes from one over half of the sixth to one over half of the third and that's exactly why we see at these high energies molecules come together they come in close proximity and by virtue of their self formalization they get the dipole-dipole interaction but as the molecules or as the energy goes down the molecules are further and further apart and at some point the self-polarizing effect can no longer sustain itself and that is exactly the reason why you see this problem until it has to go through which is a fundamental pressure rule so it also needs to go around and this is what we see here experimentally we see maybe the onset of this but it's mostly here so why then did the skepticism talk about this in the next slide and how we will react because I would like to say in one minute the development of the magnetic analog of these machines this is just a manipulation of molecules using magnetic fields we have built that over the last few years in Miami it works really nice in the up-to-specs it is very simple to know what is very cheap it consists of permanent magnets very simple colors and very trivial and very cheap electronic so it is something that everybody should be able to build and so we go back to work we get some very nice images with this machine so just to calibrate it but most importantly we can now tackle species that you cannot do in a stock assembly simply because most of the species have an electric algorithm that most have, in particular radicals have a magnetic algorithm and so this machine was really constructed with the idea of starting to react this way it was along the question line of a lot and it contributed to real chemical reactions and now we can so this is a very first proof of principle demonstration for the Zeeman decelerated sulfur atoms and we can see that he stayed scheduling with him, making real reactions and he broke the SD radical that is coming out of this reaction and this is a recent effort that we led by Lime Holdenberry a new hire in our department he is a assistant professor and he is using this project so you can see here at first we have enough data for these reaction products and it is now a functional solution and of course the whole place and the really contemplating the approaches they would have and still see a chemical reaction learning that brings me to the end of my talk but to acknowledge all of the people that are here on the work and so we have seen the tutorial in the entire group behind all our possibly machine and with that, I would like to thank you