Special Issue Preface pubs.acs.org/JPCA
Autobiography of Terry A. Miller
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Sommerfeld Scholarship but I got a summer research job in Ralph Adams’s laboratory. He was truly inspirational, often arriving in the lab sockless at 4am in the morning. He was undoubtedly the person who taught me how to do research and created my love of science. He is now remembered as an outstanding bioanalytical chemist (for whom the Adams Institute at KU and the R. N. Adams Award in Bioanalytical Chemistry presented at Pittcon are named). However, when I was in his lab, his research involved the electrochemistry of organic molecules. Since electrochemical processes often produce free radical intermediates, Ralph Adams was able to obtain a grant for one of the first commercial electron paramagnetic resonance (EPR) spectrometers, with which I was able to do experiments. This was my first encounter with either spectroscopy or chemical intermediates, two themes that have permeated my research to this day. Working in the lab full-time for three summers and part-time for three academic years allowed me to amass a half-dozen publications by graduation. These publications, a wonderful KU honors program, and an unblemished 4.0 grade point average all contributed to my being named KU’s first Marshall Scholar. (Marshall Scholarships share much in common with the older and somewhat better known Rhodes Scholarships. They differ in that Marshalls can be held at any U.K. university, whereas Rhodes are restricted to Oxford and funded from the bequest of Cecil Rhodes and Marshalls are funded by an Act of Parliament in gratitude for the support the U.K. received from the Marshall Plan following World War II). I took my Marshall at Cambridge, which again opened a whole new set of opportunities. On the cultural side, being a Marshall Scholar had many advantages. For example, at our orientation in London, we received a personal tour of Parliament from an M.P. Several times during my stay, we had formal dinners at London Guild Halls. Being a Marshall Scholar also meant a few brushes with Royalty. Once at Government House on the grounds by Buckingham Palace, we were served on the Queen’s official china bearing the royal emblem with the initials, E. R. (Elizabeth Regina). A number of years later, I had an opportunity for a nice chat with Prince Charles at the British Embassy in Washington. Of course, living in Europe afforded me opportunities to enjoy visits to many well-known castles, cathedrals, etc., which were certainly more historical, ornate, and older than anything in Kansas. Most importantly, the Marshall Scholarship allowed me to join the Theoretical Chemistry Department at Cambridge University. At that time, Chemistry had four professors, each with his own department, with separate stores and shops. Interaction among them was minimal, including between theoretical and physical chemistry. Obviously, things are different at Cambridge today, and a number of years after I
was born in Girard, a farming community of about 2500 (then and now) in the southeastern part of Kansas. I was the only son of a single-parent mother, a situation less frequently encountered then, especially in rural Kansas, than now. However, my mother lived in my grandparents’ home, and I enjoyed a loving and supportive childhood. After my fourth year in school, my mother remarried, and we moved even farther into the southeastern corner of Kansas to Baxter Springs. Baxter was about double the size of Girard and had somewhat more repute (ill or otherwise) from being the “first cowtown” in Kansas, as large herds from Texas were driven through there briefly in the 1860s and 1870s; later in the first half of the 20th century, it served as a boisterous center for the surrounding zinc and lead mines, metals of considerable value during the two World Wars and the Korean War. However, by the time I arrived in Baxter, the value of these metals had dropped to the point that it was insufficient to keep the mines open and the local economy prosperous. My time in Baxter was mostly enjoyable, playing sports like most teenage boys, but recognizing that I enjoyed school more than many of my classmates. Baseball was my favorite sport, and I was good enough to make the town traveling team and often played on the same fields where Mickey Mantle had played less than 10 years earlier. This experience taught me a valuable life lesson. I realized that no matter how hard I tried, I never was going to hit the ball as far as Mantle had. While I really wanted to play major league baseball, this experience convinced me that I had better prepare for another line of work. My high school guidance counselor advised me, along with the others in my class (graduation size, about 50) who were interested in college, to attend Pittsburgh State Teachers College, about 20 miles to the north of Baxter Springs; however, I was determined to go “big time” to the University of Kansas. My mother and I talked considerably about the financial aspects of this goal, and things did not look too promising. Fortunately, my SAT scores were sufficiently high to attract an offer of a partial scholarship from KU, and my mother agreed that there was enough money for me to attend KU “at least the first year”. The scholarship that I received was a position in a Scholarship Hall, an institution effectively unique to KU. The residents of Scholarship Halls paid for their education with “sweat equity,” cleaning the dorm, cooking the meals, etc. With this arrangement, the full cost for room and board was ∼$40/month and tuition then was ∼$75/semester, which made things manageable, but still financially challenging. Fortunately, based upon my academic performance my first year, KU awarded me a Sommerfeld Scholarship, providing a full ride since I continued to live and work in the Scholarship Hall. I cannot overestimate the importance of my time at KU and the doors that were opened to a world which a young man from rural Kansas had never imagined. KU operated at a quite different intellectual level from what I had hitherto experienced, and I was exhilarated by it. Truly, the turning point for me was right after my freshman year when not only did I receive the © 2013 American Chemical Society
Special Issue: Terry A. Miller Festschrift Published: December 19, 2013 13209
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graduated, I had the singular honor of returning to give the first joint physical−theoretical seminar. Notwithstanding the fact that I was in the Theoretical Department, I worked for an experimentalist, Alan Carrington, later to be named a Fellow of the Royal Society and Commander of the British Empire. However, at that time he was (just) a member of staff (not faculty) and an Assistant Director of Research. There were no Directors of Research at Cambridge because at some point in the institution’s long history, one of the Professors had stated that only he could direct research; anyone else could only assist in its direction. Alan was an ideal advisor for a new graduate student. He was extremely enthusiastic and a clever and tenacious experimentalist. When I arrived at Cambridge, Don Levy was already there as a postdoc in Alan’s group, and the three of us spent many long hours together in the lab where I had the wonderful opportunity to learn from two great mentors, Alan and Don. It also taught me the advantage and joy of cooperatively solving scientific problems. Once the first gas-phase EPR experiments started working, data readily flowed, and a series of papers were published with the authorship: Carrington, Levy, and Miller. Although the order may seem a little unusual these days, in the U.K. at that time, listing authors alphabetically was not unconventional. Alan endorsed that tradition and only once made the mistake of accepting a student whose last name began with A or B. The Professor of Theoretical Chemistry at that time in Cambridge was H. Christopher Longuet-Higgins, F.R.S. He was enormously intelligent, as demonstrated by the fact that he developed the concept of the 3-center bond for B2H6 as an undergraduate at Oxford, and at Cambridge applied permutation−inversion group theory to chemistry and developed the concept of the molecular symmetry group. He was kind but also the archetype of the Oxbridge Professor. He personally approved line by line every research paper written in his department. I remember several times sitting with Alan in the Professor’s office going over a manuscript line-by-line, with him clarifying the science, improving the English, and, somewhat to my irritation, changing my American spellings to “proper” British ones. As mentioned above, I had taken and analyzed the EPR spectra of a couple of organic free radicals in solution while an undergraduate at Kansas. Alan Carrington also had an EPR spectrometer and used it to obtain condensed-phase spectra of both inorganic and organic species, but as appropriate for the Department, took a strong interest in what information such spectra could shed on theoretical topics such as hyperconjugation, Jahn−Teller interactions (upon which LonguetHiggins also had written seminal papers), etc. It was, in fact, this combination of theory and experiment that had attracted me to work with him in the first place. When I arrived at Cambridge, Alan had just gotten a new EPR spectrometer with a large magnet capable of fields of 15 T, much larger than necessary for traditional EPR spectroscopy with an X-band frequency source. However, Alan did not plan to do traditional EPR in the condensed phase; rather, he wanted to do gas-phase EPR on paramagnetic, open-shell molecules. To put this idea into perspective, it is useful to recall the state of spectroscopy in this frequency range at that time. For over 20 years, post WWII, microwave spectrometers had been cranking out the rotational spectra of hundreds of molecules. Excepting the relatively nonreactive O2 and NO, the microwave spectrum of essentially only one reactive, open-shell
molecule, the OH radical, had been reported. The reason for the paucity was that it was generally impossible to fill a long microwave waveguide with the necessary concentration of a reactive, gas-phase species to record its spectra. In my experience, the most significant scientific advances come from a combination of at least three elements: inspiration, ignorance, and serendipity. One needs the inspiration to visualize a new experimental approach or theoretical concept, the ignorance not to know that conventional wisdom argues that it will certainly fail, and the serendipity that the ignorance does not destructively interfere with the inspiration. The gas-phase EPR project had all three of these elements. (i) The inspiration was that the multipass characteristics of the microwave cavity of an EPR spectrometer enhanced sensitivity and significantly reduced the volume of the sample of reactive species needed, thereby overcoming the basic obstacles that had previously blocked the obtainment of microwave spectra. (ii) The ignorance was of the details of how electric (necessary for sensitivity) and magnetic (traditional for EPR) dipole transitions differed in the ability of a magnetic field to tune them into resonance with the microwave frequency. (iii) The serendipity was that ignorance of the lack of tunability did not, in fact, eliminate observing gas-phase EPR spectra, but did limit the application to open-shell molecules for which significant coupling between the electric and the magnetic dipoles existed. Fortunately, a number of very interesting reactive intermediates exhibited sufficient coupling for us to observe their EPR spectra, including SH, SF, SeF, SO, SeO, ClO, BrO, and IO, as well as measure the electric dipole moments of the latter three. These results gave me more than sufficient material for my Ph.D. dissertation. Another milestone in my life had also been accomplished by this time. In the summer, between my first and second years at Cambridge, I flew back to Kansas and married Barbara Hoffmann, who had just completed her undergraduate degree at KU. Ever since, she has been my constant companion, my inspiration, and the producer of our two wonderful sons, Brian and Stuart. Brian is now a lawyer, lives only minutes away from our home, and has provided Barbara and me with 3 adorable grandchildren. Stuart is an M.D., practicing in Charlotte, NC, and has also provided us with 3 adorable grandchildren. A year later, happily married and having nearly completed my Ph.D., I was ready to look for a job. Unlike today, it was not deemed necessary to have postdoctoral experience, even for an academic job, and that was good because jobs were still quite readily available when I was looking. However, 18 months or so later they were not, as the first cutbacks in Federal research spending were occurring due to the continuing Vietnam War and the U.S. beginning to experience a mild recession. After Barbara and I spent all night reveling at a May Ball in Cambridge, I hopped on an early morning train to Heathrow Airport to fly back to the U.S. for interviews at four universities and Bell Telephone Laboratories (later AT&T Bell Laboratories). Fortunately, I got several offers and had a tough decision, finally deciding in favor of Bell Laboratories, when a part-time teaching position at Princeton was added to the offer. During my time at Cambridge, I was always impressed by the caliber of the “intellectual firepower” there. When I went to Bell Laboratories, I was impressed by both the caliber and the volume of the firepower. At its height a few years after I joined, it was a research institution roughly 20 000 strong, including support personnel. Of course, the basic physical scientists constituted less than 10% of the scientific and engineering staff, 13210
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About this time, I realized that the most interesting transitions to observe in light atoms or molecules would be ones between singlet and triplet states. The energy gap between the lowest triplet and the singlet ground state had never been well determined, even for He, the problem, of course, being that such transitions are so highly forbidden in light species that it was impossible to drive them with the available radiation sources. After much thought, I realized that the spin−orbit coupling mechanism could be written as a sum of symmetric and antisymmetric terms in the individual electron spins and that the latter part would couple singlet and triplet states. If the singlet and triplet states were magnetically tuned to degeneracy, then this weak perturbation would cause an avoided crossing or an anticrossing, which could be optically detected by monitoring the emission of one or both states. The key to a successful experiment was to find a level to monitor that could be tuned to degeneracy with a level of different multiplicity by the 15-T magnet I had. After much researching the known electronic levels and a good deal of perseverance searching for a spectrum, we successfully observed the first singlet−triplet anticrossing in He. Later the same year, we found anticrossings in H2, which established its singlet−triplet separation. We made additional measurements that determined the zero-field separations of individual singlet−triplet levels to ≲10 MHz, and these results remain the standard today. These measurements were the beginning of my long-standing interest, continuing until today, in quantum state degeneracy in general and, in particular, level crossings; avoided crossings; and later, conical intersections in polyatomic molecules. The second long collaboration I had at Bell Laboratories was with Vladimir Bondybey, who was doing laser-induced fluorescence (LIF) spectroscopy on matrix-isolated molecules. We were both interested in studying radical ions, and the existence of relatively low-lying electronic states due to their open shell character made them ideal candidates for LIF, given the limitations of the lasers then available. Mass spectroscopy of ions was, of course, already well developed, but spectra of ions providing information about their internal structure, electronic or nuclear, were extremely sparse. Again, the issue was combining a very sensitive spectroscopic technique with the capability of making relatively high concentrations of ions. LIF was a very plausible spectroscopic choice for sensitivity; however, we tried with varying degrees of success several techniques for making sufficient ions. The first technique to succeed was to produce metastable rare gas atoms in an electrical discharge, which then Penning-ionized molecules. With this technique, we were able to observe the LIF spectra of simple ions such as N2+, CO+, CO2+, etc. These spectra validated the technique. A significant advance took place when we observed the LIF spectra of the cations of fluorobenzenes, which showed the vibrational structure of the excited electronic state. Shortly thereafter, we were able to take dispersed fluorescence (DF) spectra from these laser-excited ions to gain a comparable picture of the ground state vibrational structure. Concurrently using the apparatus in Vladimir’s lab, we observed even more highly resolved LIF and DF spectra of the ions in Ne matrixes where, however, the effects of perturbation by the environment could not be ruled out. At about the same time S. Leach and co-workers at Orsay were taking discharge emission spectra on a very large, conventional grating spectrometer, which had a resolution intermediate between our matrix and gas-phase spectra. The Orsay spectra were, of course, free of matrix perturbations, but
and chemistry-related folks were only about 10% of that fraction. Nonetheless, Bell Laboratories was clearly the greatest corporate research organization of its time, maybe of all time. Those of us in the basic research area had only one mission statement imposed upon us: Do outstanding work in areas which may have relevance to communications. Money for equipment was plentiful. However, unlike universities, research groups did not exist in the basic research area of Bell Laboratories. As a Ph.D. member of staff (we were all “members of staff,” including the Nobel Laureates), I could expect to have a technician, perhaps with an undergraduate degree. My technician, Bernie Zegarski, did not have a degree; nonetheless, by the time I left Bell Laboratories, he was deservedly coauthor on nearly 20 scientific publications. After one had initially proved oneself at the Laboratories, you could sometimes get support for one postdoc, and I was fortunate enough to have a truly outstanding group of postdocs work with me during my years at Bell Laboratories. The modus operandi to gain research traction was to tap into the huge volume of high-caliber researchers whose laboratories and offices lined the halls. The trick was to convince someone that together, you could do something that had never been done before. I was fortunate to have had a number of collaborations with other members of staff; however, two such collaborations stand out for their productivity and longevity. My first major collaboration was with Bob Freund, who had arrived at Bell Laboratories a year or so before me. Bob initiated the process by telling me that he had received an unusual request for help from Al Lurio, who worked for another corporate lab, IBM. He wanted to collaborate on the analysis of the RF molecular beam spectrum that he observed of the metastable A3Σ+u state of N2. Bob had been contacted because he had observed and analyzed the RF molecular beam spectrum of the metastable a3Π state of CO while in Bill Klemperer’s group at Harvard. The reason I got involved was that the N2 spectrum was dominated by nuclear hyperfine structure (which was completely absent in CO), with which I was quite cognizant from my earlier EPR work. This collaboration resulted in our publishing two joint papers with the IBM group. As far as I know, these are the only papers ever jointly authored by AT&T and IBM employees. What makes this even more remarkable by today’s standards is that the joint work and publications did not require any extraordinary administrative clearance processes. The mantra then was only “Thou shall do great science”. Once the relationship was started, Bob and I discussed the experiments in our own laboratories, mine a modified version of the gas-phase EPR apparatus I used at Cambridge, and his, a molecular beam machine in which electron bombardment was used to create highly excited samples of atoms and molecules. I was interested in obtaining gas-phase EPR spectra of paramagnetic molecules in excited electronic states, and Bob had the capability to make such states. Combining our expertise, we developed a new technique which we called microwave optical magnetic resonance induced by electrons. We first demonstrated the capability of the technique by observing EPR-like transitions in 43P He, which were detected by a change in the polarization of the emitted visible light, caused by microwave transition. This was followed by several experiments on excited states of H2. Although Bob and I were members of the chemistry division and the work was fundamentally physics and we often published in physics journals, again, there were no objections from management, even though the work had little relevance to communication. 13211
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open-shell intermediates in combustion, atmospheric chemistry, and plasma processing of electronic materials. In particular, I knew that we could now construct an apparatus capable of performing LIF spectroscopy on jet-cooled samples of transient species with a resolution of order 100 MHz, which would allow the resolution of rotational and fine structure. Such structure could both answer fundamental questions and provide unambiguous “bar-code” type spectra for species identification and monitoring. We used this system to investigate a number of free radical systems. Although this is not the place to delve into all those results, systems investigated included the following: cyclopentadienyl and its methyl and CN derivatives; benzyl and its methyl derivatives; a series of half-sandwich organometallic complexes, X·R, with X = Mg, Ca, Cd, and Zn and R = C5H5, C5H4CH3, C5H4N; metal monomethyls, XCH3, with X = Mg, Cd, and Zn; the alkoxy radicals, CRR′R″O with R, R′, and R″ being alkyl groups, H, or D; and radical complexes such as Rg· OH and Rg·SH, with Rg an inert gas. The most unifying theme of these studies was that nearly all these species were intermediates in some reaction of significance, socially or economically. In many additional cases, their high resolution spectra displayed characteristics or combinations of characteristics (rotational, spin-rotation, spin− orbit, torsional, or other large amplitude motion, etc.) rarely if ever previously observed or analyzed. In the early days of this work, estimation of the molecular parameters determined by the spectral analyses was well beyond the capability of any reasonable calculation by electronic structure methods. Today, that gap has closed so that it is a true synergy between computational and experimental results. Nonetheless, spectroscopy of this nature continues to provide an experimental “gold standard” to benchmark computational work. A more specific thread in much of this research that ultimately traces back to Cambridge, but was rekindled at Bell Laboratories by our work on both anticrossing spectroscopy and symmetrically substituted benzene cations, is understanding the ramifications of electronic degeneracy or near degeneracy for both spectroscopy and chemistry. Today, mainly via computational techniques, we know the importance of nonadiabatic chemical reactions and the role conical intersections play in many of them. Because of the rapidity with which molecules pass through conical intersections along reaction paths, it is extraordinarily difficult to characterize these potential energy surfaces (PESs) experimentally. However, a conical intersection determined by symmetry, that is, a Jahn−Teller conical intersection, is different. The Jahn−Teller PES supports stationary states whose eigenfunctions probe the region of the conical intersection; therefore, spectroscopy between the corresponding eigenstates can characterize the Jahn−Teller intersections. My group has made a concerted effort to experimentally observe and analyze Jahn−Teller- and pseudo-Jahn−Telleractive molecules. Concurrently, we have developed the theory necessary to relate the spectroscopic observations to molecular properties and electronic structure calculations thereof. Jahn− Teller systems investigated include the open shell species (Jahn−Teller active state in parentheses): C5H5 (X̃ 2E1″); C7H7(X̃ 2E2″ and à 2E3″); C6F6+ (X̃ 2E1g); C6H3F3+(X̃ 2E″); CH3O, CH3S, and CF3O (X̃ 2E); XCH3(à 2E) with X = Zn, Cd; XC5H5 (à 2E1) with X = Ca, Cd, Zn; Ag3 (X̃ 2E′); and NO3 (à 2E″). Since many of these systems contain H, it is often possible to substitute D(s) or methyl group(s) to displace the
not of complicating hot bands. Most of their and our results agreed, but there were, nonetheless, some significant differences in interpretation of the spectra, particularly for the symmetrical species whose ground electronic states were doubly degenerate and subject to Jahn−Teller effects, which led to some scientific controversy. To resolve the controversy, we realized that we needed colder gas-phase spectra with less congestion and better resolution. We used liquid N2 cooling of our Penning source to significantly simplify our LIF spectra. Finally, in some of the last experiments I did at Bell Laboratories, we were able to observe the LIF spectra of free-jet-cooled ions and free radical neutrals. In concluding the discussion on the fluorobenzene cations, I should remark that the liquid-N2 and jet-cooled LIF and DF spectra largely resolved (mostly in favor of our interpretation) the earlier controversies. Moreover, I am happy to say that in keeping with the culture of the spectroscopic community, the dispute never became personal; the effort on both sides of the Atlantic was to discover the correct scientific answer. About this time the “Rock of Gibraltar” that Bell Laboratories represented as a scientific institution cracked under the pressure of the settlement of an antitrust lawsuit against AT&T, which resulted in its breakup into a number of separate organizations. I had always believed that the best way to project the future of an organization was to extrapolate its past. However, I realized that the breakup of AT&T was the equivalent of the “big bang”, and as far as Bell Laboratories was concerned, it marked a new beginning of time. Given those circumstances, I felt it was prudent to explore professional opportunities outside Bell Laboratories. My timing was again good: a recession was nearing its end; the Vietnam War was over; additional Federal money began flowing into science; and therefore, some universities were hiring. I received several offers, including one from The Ohio State University. The Ohio State offer was most attractive for a couple of reasons. The State of Ohio had established a set of chaired professorships called Ohio Eminent Scholars for which any university in the state could compete. The Ohio State University chemistry department was awarded a chair in the area of “experimental physical chemistry.” The other reason the offer was attractive was that I already knew the long history of outstanding molecular spectroscopy research at Ohio State through my annual attendance at the OSU International Symposium on Molecular Spectroscopy. While I hesitated a bit because my family had put down deep roots in New Jersey where we lived near Bell Laboratories, ultimately, it was an offer I could not refuse. My first year at OSU was a whirlwind, creating a new lab, writing my first external grant proposals, my first real experience with teaching (although I had briefly taught at Princeton and later at Stanford during a short sabbatical from Bell Laboratories), helping with the family move (Barbara did the managing), and dealing with the political implications within the University and the State of being the first and for a while the only Ohio Eminent Scholar. However, I came to Ohio State with great enthusiasm. I would have a much larger laboratory, my own graduate students, and maybe even more than one postdoc! Most of all, I was excited about the science that I wanted to accomplish. On the fundamental side, there were a number of questions concerning conical intersections and vibronic coupling, in general, and Jahn−Teller effects, in particular, that I felt spectroscopic experiments could now address. These new techniques could also have practical applications, identifying and analyzing the spectra of important 13212
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radicals such as vinoxy; dioxygen organic radicals, such as methyl peroxy and its derivatives; and the trioxygen nitrate radical, NO3. These species all give rise to electronic spectra with sharp, clean structure in the NIR, allowing unambiguous identification of the carriers and characterization of the molecule’s properties. We began our CRDS work by observing and analyzing the room temperature NIR spectra of the peroxy radicals, which are among the very most important reactive intermediates in lowtemperature combustion and tropospheric oxidation of organic compounds. We have observed the spectra of nearly 20 alkyl peroxy radicals. These spectra identify not only the carrier with respect to chemical species, but also the chemical isomer and, in many cases, conformeric configuration. This data has been used to establish spectral/structural relationships to predict empirically the spectral transitions of unobserved peroxy radicals. We also have obtained spectra of the peroxy radicals in a jetcooled environment to yield resolution of structure due to rotation and electron spin effects. Such structure provides a barcode to unambiguously identify the spectral carrier and benchmark electronic structure calculations for it. In addition, as we have shown recently for the β-hydroxyethylperoxy radical, we can follow excited state dynamics via spectral line broadening. We have also used the jet-cooled CRDS spectrometer to record both vibronically and rotationally resolved NO3 spectra to characterize the Jahn−Teller effect in its à state. Most recently, we have developed a dual wavelength CRDS apparatus to measure absolute absorption cross sections for reactive species and the rate of their reactions. Having described my research efforts, I would be remiss if I did not include a few words concerning my other activities. The central theme of my professional life has been the generation of new scientific knowledge. A complementary theme has been the dissemination of scientific knowledge. Foremost among the latter activities has been my role as chair of the OSU International Symposium on Molecular Spectroscopy. I took over the position of Chair for the 47th meeting in 1992. The meeting started in 1946 with H. Nielsen as Chair; K. N. Rao held this position after him. After the 46th meeting, I took over the chairmanship of the Symposium with about 30 minutes of advice from K. N. Rao (some of which I followed) and a large pile of notecards. My first task was to convert the notecards into a computer file containing the Symposium mailing list. The Symposium was the largest spectroscopy meeting in the world but had been suffering from declining attendance for about the previous 10 years, reflecting the declining activity in the kind of high-resolution spectroscopy that constituted the core of the meeting. I realized that for the meeting to remain healthy, it had to continue to attract this traditional spectroscopic core, but it also needed to embrace the new directions into which spectroscopy was evolving, including atmospherically and astronomically oriented spectroscopy as well as applications in chemistry, such as molecular identifications, reactions, and dynamics. Moreover, the meeting had to attract young people just beginning their work in these areas. Fortunately, the format of the meeting was already nearly ideal for accomplishing these goals. The meeting had for years been predominantly contributed talks. The Symposium could therefore evolve as the spectroscopy interests of those contributing evolved; it just needed a mechanism to facilitate this evolution. For that purpose, I created the International
conical intersection from its symmetry-imposed location and probe nearby PES regions by observing the pseudo-Jahn− Teller effects in the spectrum. I mentioned earlier that one of the attractions of academic life was having a group large enough to pursue more than one research direction simultaneously. This capability allowed me to follow up at Ohio State an interest sparked at Bell Laboratories. It was the application of spectroscopic diagnostics to identify and monitor reactive species in nonequilibrium plasmas that are widely used industrially for the etching of electronic chips. Optimizing the gas mixtures in these fabrication machines has enormous economic importance. It has long been my opinion that coupling basic research to such practical applications can be a genuine intellectual challenge and a win−win for both basic and applied science. Since the most important etching species in these reactors are light atoms, for example, H, N, O, F, and Cl in their ground states, it was these species for which we wanted a spectroscopic detection technique that could ultimately be made quantitative. The LIF techniques that we were using for free radical studies were sensitive enough to detect the atomic concentrations in the etching; however, there was a big problem in that the lowest-energy electronic transition from the ground state in light atoms lies in the UV, where no laser source existed. Moreover, even if there had been a laser available to drive the atoms to the lowest excited state, quantitative concentration measurements would be impossible because of radiation trapping within the reactor. The solution was to drive twophoton transitions to more highly excited states that fluoresced to essentially unpopulated, lower excited state levels. Using this technique, we made 4-dimension space-time maps of the reactive atom concentrations in the reactors. Returning to our LIF work on reactive molecular intermediates, it became clear that there was one big limitation. To observe LIF spectra, the excited state of the molecule should have a reasonably good quantum yield for fluorescence, and many molecules, particularly larger ones, do not. All molecules absorb radiation at some wavelength; however, absorption spectroscopy is usually much less sensitive than LIF, which significantly limits its application for reactive intermediates. Cavity ringdown spectroscopy (CRDS) is an absorption technique that narrows the sensitivity gap considerably and is particularly appropriate for samples such as intermediates, for which long pathlengths are not easily experimentally achievable. When considering the application of CRDS to reactive intermediates, we recognized that its sensitivity depends directly on the reflectivity of the mirrors used to form the optical cavity. Since the highest reflectivity mirrors presently available are in the near-infrared (NIR) region of the spectrum, most of our spectroscopic work has been centered there, although we have occasionally ventured into the visible and mid-IR. The NIR has conventionally been viewed as a sparse region for molecular spectra, since electronic transitions typically occur at shorter wavelengths and strong vibrational transitions occur at longer wavelengths. This can be considered a negative, although it can also be viewed as a positive for obtaining clean, interference-free spectra from complex environments. Fortunately, there are a number of radical intermediates involved in the oxidation of organic molecules, both in our atmosphere and in combustion environments, with electronic transitions in the NIR. These include the unsaturated mono-oxygen organic 13213
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inevitable for the AT&T Corporation that created Bell Laboratories. If it had not been broken up by political and judicial forces, it would have been altered beyond recognition by the communications revolution itself created. Nonetheless, it is tragic that an enormously successful institution with the sustained funding necessary to create the best in science and technology, over a decades-long perspective (rather than an election cycle or quarterly report), no longer exists in that form today. The future of not only those of us involved in science and technology but all of society is less bright because of its demise. My career at The Ohio State University has had many dimensions beyond that of the research that I have described. Of course, every year since I came to Ohio State, I have taught classes ranging from general chemistry to advanced spectroscopy. Finding the way to communicate a concept that is new to a student is almost as exciting as discovering a new concept in one’s own research. However, I have been involved in many other rewarding activities at Ohio State. For several years, I have chaired the President’s and Provost’s Advisory Committee. This has been a most interesting experience. Advising highlevel administrators is one thing; convincing them to follow the advice is quite another. Recently, I served for 5 years on Ohio State’s Athletic Council, which has been one of the great learning experiences of my life. However this is not the place to discuss what is right in college athletics or what is not. In conclusion, I want to thank a few people for their wonderful help over the years. Particular thanks and gratitude go out to my long-time assistant, Becky Gregory, both for work with the Spectroscopy Symposium and for my Ohio State duties. She has always exhibited a can-do spirit, optimism, and calmness even in times of the greatest crises. I want to thank all my faculty colleagues, particularly the ones with which I have had collaborations, and the local members over the years of the Executive Committee of the Spectroscopy Symposium: Frank DeLucia, Anne McCoy, Eric Herbst, Russell Pitzer, and Weldon Mathews. Particular thanks go to Andrew Ellis and Mike Heaven for being the Guest Editors of this special issue and Anne McCoy, editor of The Journal of Physical Chemistry A, who approved and organized it. The times when Mike and Andrew “post doc’d” with me exemplified the kind of experience of which mentors often dream but rarely experience. Anne is the kind of faculty colleague of whom we always dream but rarely experience. In writing this account, I have omitted naming individually my graduate and postdoctoral students who, indeed, were the most responsible for the work described. I felt it would be unfair to mention a few when so many would go unmentioned due to lack of space. All their names are given in “Colleagues of Terry A. Miller”, which follows, and their publications are listed in “Publications of Terry A. Miller”, which follows the list of colleagues. Nonetheless, I want to say to them that I am most, most grateful for all their work and help. Without their efforts, there would be no reason for this special issue. Finally, I want to thank my family. As I mentioned earlier, my wife, Barbara, and I have two sons and now six grandchildren. Sometimes, scientists are distracted by family problems; I have only been strengthened by my family. I have always felt that it was my duty to make them as proud of me as I am of them. I cannot close without a few special words about Barbara. Although not a scientist, she has completely embraced and supported my life as one. As an example, before we had the automated production of the Spectroscopy Symposium Book of
Advisory Committee, upon whose advice I relied heavily, particularly for choosing the half-dozen plenary speakers invited and the three mini-symposia topics featured each year. Another key decision for the Symposium’s success was to hold fast in the face of a different sort of evolution. During my early years as Chair, as meeting sizes grew, there was a strong movement toward putting contributed presentations, typically from young investigators such as graduate and postdoctoral students, into poster sessions. Instituting poster sessions at the Symposium was vigorously discussed at several International Advisory Committee meetings, but always rejected. As a result, the number of well-known scientists who have given their first talk at the Symposium has continued to grow. The health of the Symposium has been maintained by a continuous flow of new people and ideas into it each year. I also think that this decision has increased the productivity of numerous spectroscopy laboratories around the world. At least I know that my students are always most productive in the time between the March 1 abstract submission deadline and their oral presentation at the Symposium. In June, 2012, at the International Advisory Committee meeting, I announced that I would chair the 68th Symposium in 2013, but would step down thereafter. A subcommittee was formed to identify a new Chair and, as it turns out, a new venue. Several impressive proposals were received, and after a difficult decision, the proposal of Ben McCall and the University of Illinois was chosen by the subcommittee and approved by the entire International Advisory Committee. I look forward to attending many more International Spectroscopy Symposium meetings in the coming years, only not as the organizer. Another scientific meeting which very much focuses on my research interests and in which I have been very involved is the International Symposium on Free Radicals held biennially at different locations around the world. In August of 1999, Tim Steimle and I organized the 25th Free Radicals meeting in Flagstaff, AZ. (A word of advice: never organize two major meetings in the same summer!) After that meeting, we became members of the International Committee responsible for deciding upon future meetings, and in 2005, I was elected Chair of the Committee and have since solicited proposals for future meetings. During my tenure as Chair, the meeting has been held in Big Sky, Montana, USA; Savonlinna, Finland; Port Douglas, Australia; and Potsdam, Germany. I look forward to the next meeting in Squaw Valley, California, USA in 2015. Another aspect of my efforts to facilitate the dissemination of scientific information has been my role as Editor-in-Chief of the Journal of Molecular Spectroscopy since 2005. Although meetings are critical for scientific vitality, it is archival journals that present and preserve the fruits of our labor for contemporary colleagues and future generations. The past 10−15 years have probably witnessed the greatest change in the world of publishing since Guttenberg invented the printing press. Obviously, this transformation has been and will continue to be a challenging time for all involved; nonetheless, this also means it is a time of opportunities and an exciting time to be an Editor; however, I believe the core values of making the scientific literature reliable, accessible, and permanent must continue to prevail. Finally, I want to remark briefly on the two places where I have worked since my Ph.D.: Bell Laboratories and Ohio State. There never has been a better place for science and technology than Bell Laboratories was at the start of my career. Change was 13214
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Abstracts, she would literally cut out the mailed abstracts and paste them and typed titles on large pages which would be photographed for the printer. For the past 28 years, she has been a wonderful hostess (preparing all the food herself) for the Chair’s Reception at our home each Tuesday evening of the Spectroscopy Symposium. She has always welcomed my students into our home and hosted at least two parties for them annually. Since our children left for college, she has been a frequent companion of mine at scientific meetings around the world. I am fairly sure that she is the best-known nonspectroscopist at these meetings. Most of all, I thank her for being my life-long companion, support, and inspiration.
Terry A. Miller
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