Robert Baker === David Staley: When you were a kid, did you know you were going to be a physicist and that you'd be working in this kind of setting? Robert Baker: There's no way I could have envisioned this facility. But I loved playing with light. I had a laser tag. And rather than playing laser tag with it I would set up a series of mirrors around the house And I would align my laser tag to see how many bounces I could get and still hit the target so that's actually was great practice for aligning these complicated optics. ​Jen Farmer: From the heart of The Ohio State University on the Oval, this is Voices of Excellence from the College of Arts and Sciences, with your host David Staley. Voices focuses on the innovative work of Arts and Sciences faculty and staff with departments as wide ranging as art, astronomy, chemistry and biochemistry, physics, emergent materials and mathematics and languages, among many others. The college always has something exciting happening. Join us to find out what's new, now. ​ David Staley: I'm pleased to be joined today by Robert Baker, Professor in the Department of Chemistry and Biochemistry at the Ohio State University College of the Arts and Sciences. His research focuses on the critical role that surface electron dynamics and interfacial charge transfer have on the selectivity and efficacy of catalytic energy conversion processes. Dr. Baker, welcome to Voices. Robert Baker:Yeah, thank you David. Welcome to the NeXUS Laboratory. David Staley: I was gonna say, you should be welcoming me, because we are right now in the NeXUS Laboratory. First of all, tell us, what is the NeXUS Laboratory? And then you're gonna give us sort of an audio tour. Robert Baker: The NeXUS Facility is a unique in the nation infrastructure investment by the National Science Foundation. At the heart of the NeXUS Facility is a first of its kind laser in the United States that drives the process high harmonic generation. This is a process that was recently recognized by the 2023 Nobel Prize in Physics, which was shared Professor Emeritus Pierre Agostini. David Staley: From here at Ohio State, yes. Robert Baker: In the physics department at Ohio State. And this is a very promising and powerful technology that allows us to produce extremely short pulses of extreme ultraviolet and soft X ray light that then we use to interrogate electron and molecular dynamics in all sorts of chemical molecules and materials. David Staley: Tell us what NeXUS stands for. Robert Baker: NeXUS stands for National Extreme Ultra Fast Science Facility. The term NeXUS didn't appear in our original proposal, and when NSF decided to fund this, one of the first things they told us is, Okay, we need a great acronym to brand this facility with. And so we actually held a contest amongst the students who were gonna help build the facility, and the students actually coined the term. David Staley: Good for the students. Robert Baker: So, we're gonna walk around the lab here in just a bit, but first of all this is the laser right here. David Staley: This is the laser. So, what I'm looking at is it looks like a bunch of file cabinets laying on the side. Robert Baker: Okay, yeah. David Staley: Which is maybe not the most poetic way to describe it. Robert Baker: Right. Okay. so this, is the CPA. We call this a chirp pulse amplifier, but the laser actually spans this entire length. So see we have about 15 feet here. David Staley: Yes. Robert Baker: And about 30 feet here. This whole thing is the laser. So maybe to give you a comparison, the laser in my lab produces about five watts of power and this laser produces over 800 watts of power. David Staley: So just give a verbal description of what we're looking at here. I gave a clumsy definition of this down here. What are we looking at down here? Robert Baker: So actually the boxes that you described as a file cabinet, there's actually 16 fiber amplifiers. Each one of these will amplify a laser pulse. And then there's a very, complex interferometer that will coherently combine the output of all 16 fibers to create one massive laser pulse that's firing at hundreds of kilohertz repetition rate. And then as, the beam propagates through these tubes, we have several stages of pulse compression. So we can take the output that comes out here at 250 femtoseconds, which is already pretty short, And we can press it down to eight femtoseconds. And then when we drive high harmonic generation, then we go down to sub femtosecond. David Staley: Yeah. Now I recall the last time we spoke, which by the way was six years ago. Robert Baker: Okay. David Staley: I was checking this the other day. Robert Baker: Okay. David Staley: We talked about, femtoseconds. Robert Baker: That's right. David Staley: Remind us again. The kind of scale we're talking about, how fast that is. Robert Baker: So femtosecond is 10 to the minus 15 seconds. And that was six years ago. So now, we have a new order of magnitude to describe. David Staley: You're joking. Robert Baker: So at NeXUS, we do attosecond science, David Staley: Attosecond, the attosecond. Alright, you have to explain what that is Robert Baker: Atto is 10 to the minus 18. And, and the comparison that we like to give is there's more attosecond in one second than there are seconds in the age of the universe. David Staley: I don't dunno if I can get my head around this. Robert Baker: Yeah. David Staley: So wait a minute. In the six years since you and I last spoke, we've got a whole new dimension of time. Is there a new time dimension? Robert Baker: Well, so is a rapidly evolving field and as I mentioned, atto second science was recognized by the 2023 Nobel Prize in physics. So this has been a field that's been developing for the last few decades, but it is garnering a lot of interest because of its potential right now. David Staley: And what is that potential? What sorts of, work are we talking about here? Robert Baker: Well, you know, the reason attosecond is exciting is because this is the natural time scale for electronic motion. electrons are very light and fast even compared to you know, I think, oh, you know, an atom is small. And you know molecules can react very quickly, but even compared to the atom in a molecule, electron is much lighter and much faster. So whereas molecules react on the femtosecond timescale, electrons move on the outer second timescale. And so if we really want to understand electronic motion in, say, processes like quantum computing or information processing, where you're flipping charges or spins, which are essentially electronic motion, or solar energy conversion where you're having to separate positive and negative charges. These are all processes that add their heart are driven by electron dynamics, and these are very fast processes. And so if we want to develop the technology to understand them, we have to be able to interrogate them on the out of second time scale. David Staley: So what does the laser do? What's the laser's role in that process? Robert Baker: So the laser's role is actually to produce the light needed to probe the chemical system. David Staley: Which is all a laser is, I guess, is, well, is light, right? Robert Baker: Well, yeah, yeah, a special kind of light, coherent light, where we can tailor the light to the experiment that we're trying to perform. So actually you'll see the NeXUS Laboratory, it's pretty large and we have three different beam lines and multiple different experimental end stations. And the goal of every one of these beam lines is to tailor the light in a specific way to enable a unique class of science. David Staley: So why don't we take a walk around the lab. Yeah, please. Robert Baker: Okay, so the first beamline that you see here, this is for x ray absorption and x ray reflection spectroscopy. Some of the applications that would be supported on this beamline would be, for example, studying charge separation in photocatalytics or solar materials. Looking at, spin crossover in, photochemical complexes or molecular magnets. David Staley: Spin crossover? Robert Baker: Yeah, so an electron you think of the electron as a negative charge, but the electron also carries a spin. This is like the fundamental unit of magnetism. So a spin can either point up or point down. Once you compile many of these, this is like the Pole and the South Pole of a magnet. David Staley: Okay. Robert Baker: So you know, a lot of information processing a lot of information gets stored as a 1 or a 0. But in many instances, this is a up spin or a down spin. And the ability to flip those basically tells you at what rate you can process information. And so traditional technologies might flip those. Spins on like the nanosecond timescale, but okay, could we go six orders of magnitude? Could we go a million times faster and flip spin on the femtosecond or nine orders of magnitude faster and flip spin on the atto second time scale? These are the questions that we want to ask at NeXUS. David Staley: Any answers? Robert Baker: Well, I mean, yeah, there are some very exciting results that are kind of being published in the last few years that suggest that we have not yet reached the fundamental limits. And that out of second processing is, definitely possible. And that's why scientists are excited to come and use this facility. let me take you to the next beam line. So this second beam line actually tailors the light in a different way that supports what we call ARPES. That stands for Angle Resolved Photoemission Spectroscopy. This allows you to see the band structure, or in other words, the way electrons distribute their energy and momentum. in materials. So there will be a lot of surface science that will happen at a beamline like this. Studying things like quantum materials two dimensional materials, transition metal dichalcogenides. So this is kind of like a very material science focused beamline in that station. David Staley: What sorts of results? Robert Baker: This is something that's unique about NeXUS is unlike my laboratory, where I get to choose the type of science that we do, the NSF invested in this infrastructure in order to make this sort of technology that we specialize in here at Ohio State broadly accessible to the entire community. So scientists from around the country or around the world will have the chance to submit their best ideas, these will be reviewed, and those that are selected for time, will get to come and, perform their experiments. So we, have exciting ideas, but, really what NSF wants to see is that the entire community is going to define the science that happens here. And toward that goal, we're actually hosting a user's workshop next week, where people from around the country will come. We'll be brainstorming together and discussing the exciting first scientific experiments that are going to happen as NeXUS opens this fall and in the coming year. David Staley: How many people are you anticipating? Robert Baker: Oh we are going to have probably 70 people in person, and then a much broader audience tuned in to some of the plenary talks online. David Staley: I'm noticing and you'll excuse me, that looks like tinfoil at the end of this. Surely that's not tinfoil. Robert Baker: Well, actually that's aluminum foil and aluminum foil comes in very handy. David Staley: Like I'd find in my kitchen. Robert Baker: Yeah aluminum foil is very clean and, it doesn't have any of the greases that we have in our fingers. And when you're doing experiments like this surface science experiments, where you need extremely low pressures, you don't want grease or dust on anything. So, any open ports that are temporarily exposed to air, we wrap them up in aluminum foil to, to keep them pristine. The last beam line is for an experiment where we'll couple XUV light to an STM. STM stands for Scanning Tunneling Microscope. Scanning Tunneling Microscopy is a technique that allows you to get subatomic scale spatial resolution. So you can actually resolve single atoms on the length scale of less than an angstrom. David Staley: When you say resolve. Robert Baker: I mean, you can actually, you can actually take a picture look at a photograph that shows individual atoms, and even electron wave functions, which are smaller than the atom itself. David Staley: That's extraordinary. Robert Baker: So, this, is a really challenging technique, but, very powerful technique. One of the traditional limitations of this technique, though, is although you can take the image of the atom, it's hard to know exactly what you're looking at. So you can't tell one atom apart from another. And this is where the light will play a critical role. Because if you do this measurement, but now you do an under illumination of our soft X ray light, and you can tune this light to go above and below a specific transition that's unique to a certain element, now we can kind of impart a contrast. Or in other words, we can make every different element in the image pop out as a different color. So now you not only see the spatially resolved image, but now you can know exactly what atom you're looking at. David Staley: I can imagine what the uses are, the value of this. I mean, aside from, pretty pictures. Yeah. How will, physicists be using these? Robert Baker: Well, you know, so if you think about solid state devices, you often have to put dopants into a semiconductor. A dopant, okay, this could be like phosphorus. Okay. in silicon, or boron in silicon. you have this in your phone. this is in the microphones that are clipped to our lapels. This is how we process information right now. It's by electronic circuits that are built out of dope semiconductors. But then it's often hard to actually go down to the scale of an individual dopant atom in a semiconductor and actually see how are the electrons moving at that specific atomic site. That's the sort of measurements that we'll be able to do at this end station. David Staley: I can't even begin to describe how intricate and complicated this is. And I suppose the question I have is, Who built this? Robert Baker: Well impressively, this was built by graduate students, postdocs, and research scientists here at Ohio State University. David Staley: You have to describe that process. I wouldn't even know where to begin. Robert Baker: Well this, this is really an incredible story because when we first envisioned this facility and began writing the proposal to the National Science Foundation, this was in 2018, and we were one of nine mid scale facilities selected for funding in the inaugural year of this infrastructure program, which was 2019. And before we could even kind of finish celebrating receipt of this award COVID hit and we went into lockdown. And so basically our team was tasked by taking relatively young graduate students and some postdoctoral scholars and trying to work remotely and begin the So, know, *this existed in AutoCAD before any of these vacuum chambers or wires or feed throughs were ever fabricated. And this, all happened during the last five years thanks to the devoted efforts of some really talented students and postdocs. David Staley: Who designed that? Who created the AutoCAD version of this? Robert Baker: This was done by the students, postdocs, and outstanding research scientists that we have here at Ohio State. Just all of them. That's just amazing. Yeah. David Staley: And so, is that part of one's training as a physicist, in other words, are you trained to also be a, I don't know, a construction engineer? Robert Baker: Well you have to wear many hats when you take on an endeavor like this. But that's actually one of the things that motivated this program, from the perspective of National Science Foundation, is they recognize the importance of workforce training. to be able to construct instrumentation and, design these very cutting edge experiences. And actually, this is an area where the United States has traditionally lagged behind Europe and other countries in investing in this sort of infrastructure. And so, one of the things that National Science Foundation finds attractive and that we're really proud of here at Ohio State is that this facility is providing that type of workforce training to students here. David Staley: When you say workforce, what other sort of applications outside of this laboratory, outside this university, Robert Baker: The laser, which is the heart of the NeXUS facility, the place where it finds its biggest application is on manufacturing floor. So these really high average power ultra fast lasers have a lot of applications and some of these are in, laser processing and machining and fabrication. David Staley: Why does the U. S. lag behind Europe and other areas? Robert Baker: You know, there, there have been a number of reports. So there is a landmark report that got published in 2018 called Reaching for the Brightest Light. This was a report by the National Academies of Science. Lou DiMauro, who's professor of physics department, played an important role in this. And one of the things that these reports have documented is that in the United States we have a certain funding, platform, which does a very good job of funding individual principal investigators like me and my own research laboratory and many others here at OSU. And it also does a good job of funding large scale facilities like synchrotrons the x ray free electron laser at, SLAC. So we're talking about large DOE facilities. Department of Energy. Department of Energy facilities. But between these two extremes, there's a gap, which NSF has titled Mid Scale Research Infrastructure. So this refers to things that are bigger than a single PI laboratory, but still much smaller than like a 1 billion investment by the Department of Energy in a synchrotron facility. And so this is something that in other countries has been part of the culture of science and built into the funding portfolio, and in the United States, we kind of recognize that this has been lacking and so the NSF and other funding agencies have been very enthusiastic at responding to these reports and this is one of their responses and so in the way it creates a new paradigm for science here in the United States, which is highly collaborative. So, for example I'm not necessarily an expert at quantum information processing, but I am good at designing femtosecond and attosecond light sources. So what can I do in collaboration with the material science expert who has very promising material for quantum information processing, but they need to understand electron dynamics in this material? And so we envision this being like a center point for interdisciplinary collaboration where we provide the light and the local expertise to operate this very complicated infrastructure. But people come from all over with their own scientific questions. And they're going to help us define what science we do here. David Staley: So, that's what you meant by mid scale. I was going to ask you that question. Yeah, mid scale. What's meant by mid scale? Robert Baker: Mid scale, so we're bridging this gap between something that's too big too complicated. For me to do with just my own few graduate students in my own research laboratory takes the investment of an entire community, but still is not the construction of a full DOE National Laboratory. David Staley: And maybe you indicated this earlier, why was Ohio State chosen for this? Robert Baker: Yeah, well, that's a great question. I think Ohio State was chosen largely because we have a great team here that provides the local expertise. So the National Science Foundation wants to put this in a place where the host institution of Ohio State can support the user community at being successful at these experiments. We need the local expertise. So this is a place where we have long standing expertise in attosecond science, the Pierre Agostini-DiMauro Laboratory that was recognized by the Nobel Prize. We have Roland Kawakami, And Jay Gupta in physics who are experts in their ARPES and STM measurements, Claudia Turo in chemistry, who's a renowned photochemist and our expertise in the light sources. So we, provide the local expertise and support the NSF thinks is going to be critical to supporting the users that will come in and be here at NeXUS with us. David Staley: You and I are wearing lab coats. I'm wearing a hair net. I'm also wearing a beard net. And I'll say I don't wear a beard, but I am a couple of days scruffy here. Why am I wearing all of this? Robert Baker: Yeah, so NeXUS is a clean room. There are some optics which are exposed to air and they're illuminated by this very high intensity light. And so any dust that could land on these optics would irreparably damage them. Some of them are extremely expensive. They have long lead times. And basically to protect this highly sensitive equipment, we keep dust in this room to an absolute minimum. David Staley: I am not wearing the goggles that I saw. Okay. Those are outside as we were getting dressed. Right. And maybe it seems self-evident. Why would I have to wear goggles in here? Well, yeah. And they're special goggles. Robert Baker: They're special goggles. when the laser's on. You for sure need to have the laser glasses on because, as I mentioned, this is a really high power laser, I mean, first of its kind in the United States. so the, goggles that you wear have interesting colors. These are specifically designed to protect your eyes from the different wavelengths that might be out on the experimental table during the course of any given experiment. David Staley: Yeah. And in fact you actually wouldn't allow me in here. I'm guessing I'm not certain I would want to be in here. Robert Baker: Yeah. I'm not sure you would want to be in here if the laser were operating, but we, have some really talented and well trained staff. And so, you know, it's under their supervision that the lasers are operated. David Staley: Tell me about your involvement in this. Why were you involved in this whole process? You say it's a collaborative effort. Robert Baker: Right. David Staley: Why Robert Baker? Robert Baker: Well my group had the opportunity to be involved in pioneering some of the techniques that we're now making accessible to the community. So in a sense to me, this is a community validation of the potential impact of the sort of techniques that we've been working hard to develop in my laboratory, basically utilizing this type of light to make measurements and photo catalytic and solar materials, and kind of demonstrating to the community how powerful these types of measurements can be in terms of understanding what are the real physical processes that control the performance and efficiency of this really important class of materials. David Staley: You mentioned graduate students and others who worked on this and obviously the research implications are, immense. This in no way is involved in teaching. This lab is not involved in teaching, or perhaps it is. Robert Baker: Well, not, not in the classroom sense. So we, don't host undergraduates here, although we have had some undergraduate researchers contribute in some important ways to the development of the facility. But no, this is more of a laboratory setting where you're really getting very unique training and experience in exposure to instrumentation and lasers and experiments that are really only done at a handful of places worldwide. So I'd say it's more of a laboratory training experience, where the people who work here come out with unique skill sets that probably only a few places in the whole world can provide that sort of training to students. David Staley: What's the research horizon look like? What are you going to be working on going forward here? Robert Baker: Our goal is to show the power of this facility to the research community. You know, what I would consider a great success is that in six months or a year from now the NeXUS facility becomes oversubscribed, meaning that there are more people wanting to use the facility than we could possibly accommodate. This would send a message to the funding agencies that this was a great investment and that more of this type will be needed in the future to meet the scientific demand. David Staley: How will those decisions be made? Robert Baker: Yeah, so that's something that we're discussing with the NSF right now But they want to see that this is a really open and accessible and transparently operated facility and that's done with the help of user committee a really high quality scientific advisory board, a lot of strong institutional support from the university it's incredible the number of people supporting this in various ways to make this successful. David Staley: What's the organization of the lab? is there a CEO? Robert Baker: there's no CEO, but there's a director. I'm the director as we transition to operation and maintenance. Lou DiMauro and I were co directors during the construction phase of this facility. And there's a facility manager who's TJ Ronningen. And then we have our research scientists and staff. I told you that we involved a lot of graduate students and postdocs. That was during the construction of this. Now that this opens as a user facility, now the role of graduate students and postdocs will be to propose experiments and do experiments here. But NeXUS is really what it's going to employ as a full time staff of dedicated scientists and technicians who are qualified to operate the equipment, support the users, and then faculty, students, postdocs, and researchers from around the world will now be the proposals. They'll be the science drivers. They'll write the proposals. They'll come and collaborate with our scientists and staff here to make the experiments a reality. David Staley: What's your job as director? Robert Baker: My job as director is to make sure that the facility serves the needs of the user community and make sure that the science work pursuing is really high impact that basically we meet the vision that kind of motivated this investment five years ago. David Staley: And probably looking for more funding as well, I suspect. Robert Baker: Well, I think that that is forthcoming. The NSF has been a strong supporter of this, and they've communicated that this sort of mid scale research infrastructure is going to be key to their portfolio moving forward. So I think this is the beginning of a long partnership between Ohio State and the NSF. David Staley: Now that the laser is installed and operational, what's next? What else is going to be added to this lab? Although as I'm looking, I don't know if there's much space here. But are you thinking about those next steps? Robert Baker: Well, yeah, definitely. So as you can see, this lab is full, so It's pretty full. right now what's, you know, our highest priority It's actually now use the recently installed laser to actually demonstrate the experiments that this was designed to support. And then, of course, we're interested in growing the facility and offering the next generation. I mean, the National Science Foundation and, of course us here we want to see NeXUS stay at the cutting edge. As I mentioned, this is a rapidly evolving field. And so what the cutting edge looks like today is, going to look different five years from now. And so we have the benefit of being at the very tip of this field. And, okay, it's going to take a lot of creativity and hard work. But I think the next five years is going to be exciting. David Staley: I can't recall if I asked you this the first time I interviewed you. When you were a kid, did you envision yourself doing this? Did you know you were going to be a physicist and that you'd be working in this kind of setting? Robert Baker: There's no way I could have envisioned this facility. But I loved playing with light David Staley: Is that so? Robert Baker: Well, you know, I remember I had a laser tag. That's when I was a kid and rather than playing laser tag with it what I would do is I would set up a series of mirrors around the house And I would align my laser tag to see how many bounces I could get and still hit the target so that's actually was great practice for aligning these complicated optics. David Staley: I was going to say when I think of laser, when maybe the listeners think of laser, maybe they're thinking of something like laser tag or my son used to have a board game that involved laser, which is really not what we're, you Robert Baker: know, it's not what we're talking about here. I mean, it looks pretty complicated. There's a lot of stainless steel, but if you follow it these mirrors and optics they direct the light from its output at the primary laser. They tailor it. They shape it, in time and space, and they deliver it to the experimental end station. So in a way, not dissimilar to the mirrors I used with my laser tech set growing up. David Staley: How is NeXUS going to impact the university? What departments are going to be impacted by the existence of this lab? Robert Baker: Okay, that's a great question. So NeXUS is very broad, scientifically, so it touches a lot of different fields of science, and we want to create a collaborative research environment here. So NeXUS touches chemistry. It touches physics. It touches material science. It can answer important questions about ultra fast processes in biological systems. And so this is an endeavor that spans many fields of science. It touches multiple colleges at the university. The College of Engineering, the College of Arts and Sciences is the home to NeXUS and has been a strong supporter from day one. We have support from the Department of Chemistry and Biochemistry, the Department of Physics, but even Chemical, Biomolecular Engineering, Material Science and Engineering, Computer Science and Engineering material science and engineering, these are all fields that can really benefit from the tools that NeXUS provides. David Staley: Robert Baker, thank you for inviting us into your lab. Robert Baker: Thanks so much, David, it's great to have you here. Jen Farmer: Voices of Excellence is produced and recorded at The Ohio State University College of Arts and Sciences Marketing and Communications Studio. More information about the podcast and our guests can be found at go.osu.edu/voices. Voices of Excellence is produced by Doug Dangler. I'm Jen Farmer.