Autobiography of William P. Reinhardt - ACS Publications - American

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Autobiography of William P. Reinhardt Published as part of The Journal of Physical Chemistry virtual special issue “William P. Reinhardt Festschrift”.

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MY EARLY LIFE My life interests have always revolved around education, teaching, learning, music, travel, art, and books of all sorts. But it is been a complex path. Up through the first half of fourth grade at the Hillside Public School in Berkeley, CA, I was the only student not able to spell, add or subtract, or read with any proficiency. I’d been held back for a half year to repeat parts of the second grade, but as that did not seem to be of any help, I was moved onto the third grade anyway. The school said, “We do not want to embarrass Bill.” I replied, “Why would I be embarrassed?” What a log jam. Salvation was playing clarinet and saxophone in the school “orchestra,” a hobby and distraction that was to last through high school, ending with the Berkeley High Jazz Band. Still not able to add, or now to multiply or to divide either, and certainly not spell, I was suddenly reading nonstop by the middle of that fourth grade, and gobbled up The Hobbit in the fifth. I was also, to the surprise of all, often coming to the front of the classroom to reassemble into working order, and to explain to the whole class, the nature of “science demonstrations involving real equipment,” about which my teachers, through no fault of their own, had no understanding of either their hows or whys. This all changed when I was taken to Canada, France, Italy, Switzerland, Germany, and Britain in the seventh grade, traveling with my family and bioresearcher MD father who was on sabbatical at the University of Bristol in the UK, away from his usual position as Professor of Anatomy at the University of California, Berkeley. As a special guest of the highly selective Bristol Grammar School, BGS, A School Chartered by King Henry VIII in 1532, and into which I certainly would never have tested (!), I was suddenly offered the first school topic of any real interest to me, or as I would have put, even then, real importance. That was Axiomatic Euclidian Geometry. I, suddenly, and completely unexpectedly, was the “only student, out of around 150,” at BGS in the Third Form (roughly, seventh grade in the US) who was able to move ahead with complete surety and ease: never looking at any book, I simply proved every theorem directly from the Axioms. The British were stunned, and started praising the US Educational System, which had seemingly taught me to prove theorems! What a vast misunderstanding, as it was only in Bristol that I’d even learned what a theorem might be. The next year was in Djakarta, Indonesia, via Egypt, Lebanon, Pakistan, India, Thailand, and Singapore. Studying there at The British School in Djakarta meant that on my return to Berkeley (via Singapore, Vietnam, Hong Kong, Japan, and Hawaii) I was three years ahead of the US School System in mathematics, and I was not about to let go. A brief pause: what was encompassed in those visits to more than 16 countries, ‘round the world, and over two full years, during 1954−1956? Was it all airport, as it might well be today? No: it was cities, London, Paris, Rome, Cairo, and Djakarta itself, the shock of the rubble of the still bombed out © 2019 American Chemical Society

Cologne, Germany, a decade after the end of WW II, the Tower of London and the Eiffel Tower, jungles, forests, glaciers, rivers, countless and endless historical and art museums (our eyes popping, legs tiring), concerts, theaters, castles, walls from Roman to modern times, Gothic cathedrals, tiny churches on mountain passes, the Sphinx and the Pyramids, ancient temples in deep jungles, hundreds of unexpected meals with completely unfamiliar ingredients, surprising and mostly always wonderful. Then being held up at machine-gun point by a soldier at an out-of-town market, 10 months into our stay in Indonesia, being rescued by an Army Colonel in full uniform, moments later, who, without saying a word, returned dad’s stolen German camera, and who also turned out to be my father’s host as Dean of Medicine in Djakarta. Dad said, “Son, think about that for a moment.” No one in the ninth grade of my Junior High School, back in Berkeley, was prepared to deal with my mathematical background, so I was given a special appointment with a wonderful new, young, and enthusiastic Berkeley High School math teacher, Miss Ryan, whose specialty was geometry. She asked me to prove a theorem, returning about 20 min later only to announce, after a brief look, that what I’d written was nonsense. “What were you expecting?” I asked. “Well, you should have quoted theorems G and K, and then Q and Y.” “Well,” I said, “I’ve never seen the book you might be referring to, and, by the way, I choose to, whenever possible, start directly from the Axioms, thus my first drafts of proofs are often not perfectly organized, and they also often proceed following routes which you might not be expecting; so, please take another look.” She did, and I thought she might faint. “Where did you come f rom?” was her only response. Perhaps the only real answer is from the chaos of my own interior, with the blind luck of often finding myself lost in incredible and unusual social and intellectual environments, and then having to find my own way. Two years later, in the 11th grade, I (along with Paul Teller, son of physicist Edward Teller, of Berkeley, Los Alamos, and Livermore) was one of the first two students from Berkeley High to be allowed to take calculus at the University of California, Berkeley, just up the road. This was quite some good luck, as with my Berkeley K−6 record (cataloging failure at every single step of the way) being available, I was not allowed to take even a single honors course in my own high school. Paul and I did very well, and two years later 50−100 Berkeley High Seniors were routinely taking UCB Courses. My own father, still angry about my inability to spell, gave me the time of day for the first time. Skipping the next year of High School, I enrolled in UCB where (against all rules and advice) I self-invented a triple Arts and Sciences major in chemistry, physics, and mathematics, and was fortunate to have the delightful, and future Nobel Published: May 2, 2019 3617

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The Journal of Physical Chemistry A Prize winning chemist, Dudley Herschbach as my freshman chemistry laboratory instructor. From Dudley I learned that there were two ways to major in chemistry, in the College of Arts and Sciences, but also in a separate College of Chemistry, which existed as the result of luring G. N. Lewis (of the dots and acids) to Berkeley from Cal Tech; Lewis would not move without being given his own College! Dudley also taught us all, in year one and as he was a physical chemist, that there were two journals of physical chemistry: The Journal of Physical Chemistry, JPC, of the ACS, and The Journal of Chemical Physics, JCP, of the AIP. Take a look at each, he said, and you’ll know which is of interest! In those days JPC was the one missing quantum mechanics. Needless to say, that was well before George Schatz and Anne McCoy and many others of a more modern era. At the end of two full years at UCB, I received a formal letter from an Assistant Dean of Arts and Sciences stating, as I’d taken math, physics, and chemistry every single semester (and often more than one math course, as with my odd background all junior and senior level math courses were quickly available), and (mandatory) ROTC, I had only taken a single liberal arts course each semester. The letter provided a listing of rules violated and indicated that I’d be lucky to graduate in another four full years, were I lucky enough not to be simply expelled. Going straight to that smiling Dudley Herschbach, I immediately switched into that College of Chemistry, where I was “right on track,” and finished right on time.

The Head of Chemical Physics, the brilliant, and idiosyncratic physicist Wendel Furry, whose real talents, intended or not, were in the areas (a) “quantum measurement theory,” an area which at that moment in time had no possible experimental validation and so was more likely a part of philosophy, rather than physics, and (b) “maximally offending the House Un-American Activities Committee,” was away on sabbatical when I arrived in Cambridge in February of 1964. Thus, Chemistry Professor E. Bright Wilson, Jr., was the one to greet me as interim head of Chemical Physics. Lost in Mallinckrodt Hall on my first day in Cambridge, and looking for Wilson’s office, I bumped into Dudley Herschbach who had moved from Berkeley to Harvard during the prior semester. “Welcome,” said Dudley, “I’ve been expecting you!” He then not only directed me to “E.B.’s” office (as he quickly taught me to say) but also introduced the two of us, Dudley himself having earned his own Ph.D., with “E.B.” as his research advisor, only a decade before. I have no idea at all of how my time at Harvard might have evolved had I met Furry, rather than E.B., at that crucial moment, but from the first moment with E.B. the nature of my future directions in research were established, and it was clear that it would be as a member of E.B’s brand new Theoretical Chemistry Group. But first a digression:

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TEACHING AT HARVARD

With an NIH Fellowship in hand, I had no need to be a Teaching Fellow (called a TA elsewhere) but I wanted to dive into teaching, as well as learning about the mathematical underpinnings of analytic functions of a complex variable, so I set out to chat with every faculty member teaching Freshman through Junior level Chemistry courses for Harvard College and Radcliffe Students. I asked them if they could give me something “unusual and interesting” to do. “What?” they would say, usually being only vaguely interested in the teaching of undergraduates, how could there be anything “interesting” for a TF to do? TFs run laboratories, or quiz sections, to support their own education, not because it is “interesting”! What else would they do? A distinct exception was a brilliant inorganic chemist, but of a practical, rather than intellectual bent: Gene Rochow, who had invented the synthetic methods used by General Electric (GE) to make silicones and also Silly Putty. GE paid him $1 for that patent. Times certainly have changed. Rochow immediately said, “How would you like to run special problem solving tutorials for those students getting D’s and E’s on quizzes and hour-exams in Natural Sciences 3, which was nonhonors Freshman Chemistry?” (Note that Harvard folks actually know the alphabet: the letter D is followed by E, not F, but I think you’ll get the idea: the dregs!) I immediately said, “I’d jump through hoops to have that honor.” Well, by mid-semester 100% of Rochow’s 350 student class was attending my every session with, by then, very few students getting those D’s and E’s. Three years later I stayed on at Harvard, at Rochow’s instigation, as he was taking retirement, to actually take over the teaching of Natural Sciences 3, first as an Instructor of Chemistry starting in 1967, and later as Assistant and Associate Professor. Rochow also taught me the importance of, and the how-to’s of, Chemistry Lecture Demonstrations, which I enjoyed, as did my students, for the next (almost) 50 years. I even did such demonstrations in upper level Thermodynamics and Quantum Mechanics

HARVARD, CHEMICAL PHYSICS, AND A FIRST ACADEMIC POSITION In January of 1964 I’d just graduated from Berkeley and the Vietnam War was heating up. So, it was stay in school or be drafted. My College of Chemistry (CC) Honors advisor, Professor George Jura, was tough and orderly: the #1 BS student in the CC, and for better or worse I was that #1 student, always(!) went to Harvard for Graduate School (the #2 student could choose between MIT and Cal Tech, etc., etc., ...). By the way, this rigidity all quickly changed with the Free Speech Movement, which was bubbling all around, but it had yet to fully detonate, a few months later, so I applied to Harvard. The then Chemistry Chairman Bill Lipscomb, wrote me a fine letter saying that they’d love to have me in the following Fall, but they simply never accepted midyear students. What to do? C. Bradley Moore, my young, enthusiastic, and heads-up UG research advisor, said I could stay for 9 more months at Berkeley, taking no courses, and write a Thesis Masters on the theory of IR spectra of gas-phase organic free radicals, which had been my senior UG research topic. Then, suddenly, I got a letter from a Director of Admissions for the Harvard Graduate School of Arts and Sciences. “Here’s a brochure describing a very small program, usually just two or three students a year,” which she was sure would admit me, off year, were it to seem interesting. That small program was Chemical Physics. When I read about the requirements of that small program I thought I’d died and gone to heaven: take most all of the Physics Graduate Courses with Math and Applied Math tossed in, and then pick a research advisor, most likely from chemistry, or anyone else on campus doing atomic or molecular physics, which could include Astronomy and Astrophysics. My phantom undergraduate major in chemistry, physics, and math, had been reinvented at the next higher level. 3618

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and Phillip Johnson as theory students, provided that they set out in new directions, not just simple extensions of quantum chemistry that dated back to the days of Hartree and Fock in the 1930s, and he indicated that I was welcome to join this new and independent-minded group. We were encouraged to set our own paths and move in our own directions, but with one severe dictum: “Don’t get lost in mathematics, like my son Kenneth up at Cornell: he’s lost, and I don’t know whether or not he’ll ever find himself.” This being the same Kenneth who, not too much further along, was to win the Nobel Prize in Physics for his discovery of the Renormalization Group approach to the understanding of critical phenomena! Fathers and sons are not always able to see one another objectively; something I knew all too well. E.B.’s new theory group, was to expand into a much broader enterprise, as Roy Gordon and then Martin Karplus, and even myself, were to join the Chemistry Faculty over the next three years, each of us representing entirely new directions in theory. And it should not be forgotten that traditional quantum chemistry still held surprises, even at Harvard, awaiting discovery: Roald Hoffman and R. B. Woodward, with the support of the traditional quantum chemistry theorist Bill Lipscomb, were soon to elucidate the Woodward−Hoffmann rules, these being motivated by very specific and unexpected discoveries in the experimentally determined pathways of “ring closures” that arose in the Woodward group’s total synthesis of Vitamin B12. But, as a beginning graduate student, and being instructed to head into new areas, I was interested in many-body Green’s functions, which I’d learned about from Julian Schwinger, in a field theory course, where he used field-theoretic techniques to solve problems of equilibrium many-body quantum systems. Reminder: time and temperature are just analytic continuations of one another, so instead of doing quantum time evolution, as would be usual in field theory, Schwinger was doing thermodynamics at finite temperatures in the limit as the number of particles, N, approached infinity. My goal was to apply these methods to finite systems, i.e., small atoms and molecules, where the Green’s function approach did not require computation of a full wave function depending on all N variables, but a far simpler quantity depending on only two variables, and immediately giving the electron density and ionization potential and, via the time dependence of the Green’s function, the ground state energy as well. This was loosely connected, at least in spirit if not in any of the details, to the work that E.B. and Frank Weinhold were doing in developing methods for direct calculation of Löwdin’s “1matrix”; a combination of these two seemingly quite different methods ending up leading, quite a few years later, to what is now called density functional theory. I was having a hard time getting this going for Chemistry applications as I was using the grid based numerical techniques of Hugh Kelly, at the University of Virginia, developed for use in solving many-body problems via the use of Feynman diagrams. I should have been using the far simpler and more flexible matrix basis set methods of Clemens Roothaan, of the University of Chicago, who had developed the Matrix Hartree−Fock methods being used by Clementi and Nesbet at IBM Research. My first graduate student, Jimmie D. Doll, straightened me out on that, and we were off and running, with the first ever ab initio Green’s function direct calculations of ionization potentials and natural orbitals. The two us, also working with undergraduate Jeff Smith, produced work that led

classes, but both only on occasion. I’ll let folks try to guess which ones I chose.

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RESEARCH IN THEORETICAL CHEMISTRY AT HARVARD As Berkeley’s George Jura had assigned me to Harvard (he would not write to support my application anywhere else), it was puzzling to me that folks such as Enrico Clementi and Robert Nesbet, theoretical chemists at IBM Research in San Jose (where I’d been a summer research student in 1963), and the then very young Robert Harris just getting going at Berkeley all were advising me, with my interest in theory being clear, that the only place to do theoretical chemistry in 1964 was at the University of Chicago, with folks like Stuart Rice, R. Steven Berry, and John Light all taking theory into new and unexpected directions. “Nothing much new” going on at Harvard in theory they all noted. Little did they, or I, know that this was all about to change, and that that change would be led by the highly conservative E. B. Wilson, Jr. E.B. (even though he coauthored the famous and highly influential Introduction to Quantum Mechanics, with Linus Pauling in 1935) had always felt that there was no point in training young graduate students in theory. His logic was simple: a good quality student who knew how to carry out and interpret experiments could always find a place in the Chemical Industry; with top level students, of course, that simply being assumed, moving on to College or University careers. On the other hand, he told me at our first meeting in 1964: “ I’ve always thought that there would be no job awaiting for anyone but a top level student in theory, and thus it would be inappropriate to allow students to set out working towards a Ph.D. in theoretical chemistry, as many of them would have no future awaiting them.” Even Dudley Herschbach, he told me, had had to carry out, and publish, results and analysis of experiments in microwave spectroscopy, before he’d been allowed to even consider carrying out any real theoretical developments. But, he then continued, “I’ve, quite recently, changed my mind!” With the advent of computers, and with the utility of knowledge of the programming and use of computers suddenly appearing in all parts of modern technology, he suddenly saw that there would be plenty of room for the employment of students trained in theory, but who did not find places in Colleges or Universities. A famous part of the lore of those early days being the fact that AT&T Bell Laboratories would hire theoretical chemists, in preference to those trained in computer science, to join their computer based applications groups: theoretical chemists were trained to interpret computer generated data as if it were experimental data, and as such, it would be interpreted in terms of a specific underlying model, not at all simply as a stream of numbers. Such an approach often allowed quick rejection of bogus output, as not making sense within a broader intellectual framework. This method of thinking, with a specific physical model always in the background, and often one to be optimized, had proved to be highly useful in, for example, development of optimal data and telephone networks. So E.B. had, for the first time in his career, started a Theory Group, in addition to his Experimental Group that focused on microwave spectroscopy. He then told me that several of the students who’d entered Harvard in the preceding Fall semester, just 4 months ahead of me, had also indicated an interest in theory, and he’d accepted W. H. (Bill) Miller, Frank Weinhold, 3619

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month JILA Visiting Fellowship, which then merged with my becoming a Full Professor of Chemistry at the University of Colorado, Boulder, as well as an Actual Fellow of JILA. Young people do not expect to stay at Harvard, and they most often do not. E.B. had correctly warned me of that when I accepted that Instructorship in 1967. In Boulder I began intense collaborations with fellow faculty W. Carl Lineberger and James T. Hynes. That with Lineberger involved “the spectra of free radicals,” from my Berkeley days, but now with a joint Reinhardt−Lineberger Postdoc from Yale, G. Barney Ellison, a man for all and every season. Hynes and I dove into the problem of ultrafast energy flow within a single molecule starting this work with an exceptional graduate student, Ned Sibert. Another JILA Visiting Fellow Ian C. Percival got me interested in chaos theory and its quantum mechanical ramifications. Two year later Lineberger and I, and Robert Sievers, an Analytical Chemist, were suddenly, and unexpectedly, elected co-Chairs of Chemistry and off we went, and at full speed; having just hired the above Ellison, who with offers from Berkeley, Stanford, Harvard, and Yale, being thus vetted, could then, and only then, be considered for an offer in Boulder; as well as Tom Cech, who was soon to win a Chemistry Nobel Prize for discovering that RNA could catalyze chemical reactions, as well as carry genetic information. Postdoc S. V. ONeil, now back in Boulder in 2018, is helping to organize and manage a new program in Quantum Information and Quantum Computation, was also among that first group of postdocs who, having signed up for Harvard, found themselves in Boulder where I’d just moved. Research in Boulder included work in the areas of chaos theory, approximate constants of motion in chaotic systems, classical chaos and quantum dynamics, intramolecular energy flow, and properties of atoms in intense electric fields. This latter work involved extending the concept of “dilation analyticity” to include interactions with “non-vanishing at infinity” external dc and then ac fields, as well as the introduction of time-dependent methods. This work, carried out between 1974 and 1986, and working with a wonderful, and astonishingly productive set of graduate students, postdoctorals, and visiting faculty, including Ned Sibert, Charlie Jaffé, Randy Shirts, Steve ONeil, Charlie Cerjan, Mike Strand, John Broad, Debbie Watson, Derick Robb, Barney Ellison, Shih-I Chu, Peter Langhoff, John Eaves, J. J. Wendoloski, Alfred Maquet, Mike Raymer, Craig Holt, F. Borondo, Richard Hedges, Karl Scheibner, David Farrelly, John Hutchinson, Bruce Johnson, Rex Skodje, Turgay Uzer, and Richard Gillilan as well as with Professors Hynes and Lineberger, is summarized in my publication listings. An invaluable colleague in Physics, John R. Taylor, and I could almost endlessly discuss two of our joint interests imaginative teaching and instruction and quantum scattering theory John having authored a wonderful graduate level text in that area.

to papers appearing over the following whole decade, long after Jimmie had headed off for a Berkeley Postdoc with Bill Miller, including the paper, “π-Electron Theories Viewed as Parameterizations of the One-Body Green’s Function” [J. Phys. Chem. 83, 1508−1517 (1979)], which appeared in a JPC Festschrift in honor of who else but E.B. himself! But that was later, so where was my thesis? We were all, in the mid to late 1960s, interested in quantum scattering for molecular chemical reactions, but at that moment in time that was too tough a computer, and theoretical, problem for a one-person research team. So up I went to the Harvard College Observatory to work first with Phil Burke, a visitor from Belfast, and later with another Brit, Alec Dalgarno, who’d accepted a full time position in Astrophysics. All of this was about the astrophysically important problem of electron scattering from atoms, ions, and small molecules. Bill Miller had also started his career in scattering with electron−atom collisions, before moving into semiclassical approaches to atom−molecule collisions. This was, or could be, a one-person show, and as I knew quite a bit about analytic continuation and other uses of complex variables, I tacked this problem in novel ways, finally producing a rather thin thesis. Ouch: but the use of complex variables first seen there was to prove to be highly fruitful in the next few years. Four or five years later, working with my first sizable and interactive group of wonderful graduate students and exceptional undergrads, David Oxtoby, Attila Szabo, Rick Heller, Hashim Yamani, Tom Rescigno, Steve Adelman, Terry Murtaugh, and Jeremy Winick, this scattering work had exploded in many, many new directions, and I actually had new and vibrant research program started, and so did my students. Publications from 1970 to 1975, and many from there on, too, contain, or reflect, the results of this work. A key ingredient in all of this was the realization that the normal boundary conditions of scattering theory, imposed at “infinity,” could be bypassed by appropriate interpretation of data produced using only square-integrable (L2) basis functions, namely, functions that vanished at infinity. This, for example, allowed computations estimating cross sections with an infinity of open channels, including those corresponding to many simultaneously free particles: the rather complex boundary conditions of traditional scattering theory in such cases were imposed by “just skipping them,” via appropriate use of L2 basis sets.

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THE UNIVERSITY OF COLORADO AND JILA Dudley Herschbach was again a star player: Dudley was a JILA Visiting Fellow in 1969. JILA = Joint Institute for Laboratory Astrophysics, which simply means that ground based scientists do experiments in the “Laboratory” to help explain and predict astrophysical observations. The “Joint” here refers to the fact that JILA was a collaborative enterprise involving CU Faculty and Staff Scientists from the then National Bureau of Standards, or NBS, a term coined by one Benjamin Franklin, and soon to be renamed NIST, the National Institute for Standards and Technology. Realizing that my electron scattering work was already “Laboratory Astrophysics,” Dudley graciously suggested that I might be invited to give a JILA colloquium in 1969. He also then encouraged me to apply for a JILA Visiting Fellowship of my own for the winter/spring of 1972, and as everyone at JILA knew of me from that 1969 presentation, I won one. Two years later I won a second six

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THE UNIVERSITY OF PENNSYLVANIA In the summer of 1984 my wife, Katrina and I, with our two boys, James and Alexander, moved from UC Boulder to the University of Pennsylvania (Penn, hereafter) and to Philadelphia. I was enticed by a rapidly growing Chemistry Department, with that growth toward excellence and national and international recognition being a top priority of the University Administration. My wife, music teacher and cellist, Katrina was attracted by the presence of the magical Ricardo 3620

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Head of the LRSM in 1981 and continued working to guarantee that the whole was far greater than the sum of its parts. In the fall of 1985 as incoming Chair of Chemistry, I met the then, and also incoming, Dean of Arts and Sciences Michael Aiken. Aiken and I, along with Provost Thomas Ehrlich, began a series of discussions and negotiations that would run the length of my three year term as Chair. It was a fascinating experience for me to learn, starting on day one, how David had been so successful in building the thriving and exciting department in which I was now proud to be a new faculty member, as well as its new Chair. It was immediately evident that David had acted as a Head, rather than Chair, of Chemistry in that he simply ran everything there was to run, rather than being chief of an organization with rules, delegations of duties, and expectations that the whole faculty would be part and parcel of determining its own present and future. I quickly discovered, as had Kent Blasie, that all faculty, at all times, expected directions, questions answered, and problems solved by their Head. Although absolutely appropriate during the early stages of the rapid development that David oversaw, my experiences at Harvard, CU Chemistry, and JILA, where all faculty rotated in and out of various levels of leadership and committee service, thus maintaining a level and culture of awareness in the nature of departmental governance, made it evident that this was lacking in Penn’s department. Further, David’s Headship, thoroughly successful as it was, was a full time job that did not allow him the time and energy to maintain his own high quality research program; other faculty, easily seeing this, were then actively, even if unintentionally, discouraged from participating in departmental affairs. I thought that the continuation of its growing excellence now required a shift to a more normal and equitable form of faculty governance. To my surprise and pleasure, I found that Aiken, Ehrlich, and even Penn’s President Sheldon Hackney agreed with me. So we set to work. Making a short story out of three years of effort: by the time my term as Chair had ended, the department had a developing “constitution” in which delegations and expectations of duties were made clear, a thought taking us all the way back to Penn’s founder Benjamin Franklin. Further, the new position of Executive Vice Chair for Administration had been created and filled by the outstanding George Palladino; it was also agreed that the norm would be for faculty to rotate through three year terms as Chair, as then many of the faculty would either have served in the role or would realize that their turn might be quickly approaching, and thus the wisdom gained, or anticipated, from such service would be shared by all.

Muti as Director of the Philadelphia Orchestra, and the thought that our growing boys would fit well into the famous system of Quaker Schools, in and around Philadelphia. I had essentially brought three graduate students with me from Boulder, Csilla Duneczky, Dan Kerner, and Richard Gillilan. I also was fortunate to have quickly assembled a very independent group of Postdocs, several of whom had arrived with their own Fellowships, Itzhack Dana, Ilan Benjamin, Charlotte Nessmann, Bob Waterland, Masa Watanabe, Craig Martens, Siegfried Bleher, and Reinhold Blümel, and then added, a bit later, Anatol Brodsky, as a Visiting Professor from the Former Soviet Union, or FSU, with no home to return to. Having this group of experienced researchers was to my great good fortune, as just six months after arriving at Penn, the then Chairman, J. Kent Blasie, stepped down (his beamline at Brookhaven had become fully operational, and he’d found that being Chairman of Chemistry at Penn was rather more work than he’d expected) and suddenly I was elected Chairman of a Department, new to myself, and with myself only slightly known to its current members. One result of this new appointment was, as I clearly now realize, that during this seven year period at Penn, while I’m quite delighted to look back over the work accomplished, and the subsequent careers of my many fine colleagues, most of the publications are clearly traced back to work begun in Boulder in the areas of quantum and classical chaos theory, energy flow within molecules, and atoms and ions in external fields. The exception being the exploitation of classical adiabatic switching with the entropy as a dynamical invariant, which then led, at the University of Washington, to the use of adiabatic switching to calculate upper and lower bounds to finite temperature free energy changes via classical and quantum Monte Carlo techniques, and even to work on the fully quantum Bose−Einstein condensates starting a decade later on at NIST, and also UW. As I view myself, foremost, as a developer of novel methods, what had distracted me? First, I should say that it was likely a good thing to actually exploit this earlier developmental work, especially with highly talented and experienced colleagues, and often with direct connections to ongoing experiments. Second, I had, as had the Chairman before me, become fully involved in the management of a complex and rapidly changing and growing department, and in establishing its relationship to the rest of the University. This had turned out to be very different from holding the Chairmanship of Chemistry in Boulder where the department was moving along an established path, running with time tested and clearly stated rules and procedures in place, with an annually elected executive committee representing all five areas of the department, both to ensure shared governance and to keep all faculty, both younger and older, in contact, over time, with the workings of the department. The credit for developing the modern Penn Chemistry department goes, without doubt, to David White, who was its Chairman from 1966 though 1979. David was brought in from The Ohio State University, where he headed its Cryogenics Laboratory, with the explicit expectations that he would raise the research excellence of existing faculty and that he would add new faculty chosen for their high abilities in research in all areas of chemistry. Further, David was a founding member of the LRSM (Laboratory for Research on the Structure of Matter) at Penn, which combined the efforts of faculty from Chemistry, Chemical Engineering, Materials Science, and Physics, among others, with strong support from NSF programs in the area of Materials Science. David became

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THE TSRC An important digression, important for both myself and my family, had in the meantime started back in Colorado. In the early 1980s R. Steven Berry and his former student Peter Salamon had started some informal small summer workshops in Telluride, an ancient mining town high in the Rocky Mountains of southern Colorado, not yet gentrified, as was Aspen with it is major Aspen Center for Physics (the APC), the Aspen Institute, and Major Music Festivals. The purpose of their Telluride Summer Research Center (or TSRC, nowadays denoting the Telluride Science Research Center; see www. telluridescience.org, for an up to date listing of activities) was different from that of the more formal Aspen workshops and other summer workshops. The goal was to identify new areas 3621

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by folks in Los Alamos), who simply found it useful to employ the now well-developed workshop infrastructure, largely through the Telluride Public Schools, where classrooms and dining rooms were made available, a connection overseen by Telluride resident, and the TSRC administrator, Wendy Brooks. Many other groups then followed suit, including workshops on atmospheric chemistry, started by Susan Soloman of NOAA, and free radicals, this called “Radicals in the Rockies,” initially organized by Barney Ellison. This larger, and intellectually more diverse, set of groups began offering Summer Public Lectures and Lecture Series, “The R. Steven Berry Lectureships,” which over the following years have developed into a Telluride cultural mainstay, and the TSRC Public Lectures becoming those of the Pinhead Institute, taking full advantage of the growth of new facilities at the nearby Telluride Mountain Village. Pinhead is a hidden tribute to the brilliant Nicola Tesla, who’d installed ac power generation in Telluride to keep the mines from flooding in the early days.

in theoretical chemistry and lay the groundwork for their future development in terms of both methods and specific problems to be solved, rather than simply a venue for folks presenting overviews of their prior completed, and often already published work. Another key aspect was that the attendees were often young, beginning faculty, who would bring their graduate students with them, to see, first-hand, how science developed and (with luck and hard work) actually progressed. Salamon and Berry had invited Boulderites Lineberger and Reinhardt to join in, but Telluride is far from Boulder and these latter two had already established informal working relations with the ACP that allowed use of their Library and informal relations with ongoing conferences should an escape to the mountains seem like a good way to finish up a pile of papers and to get them submitted to appropriate journals, which in those long ago days was done via air mail; and, with a hike or two in between. So “why Telluride?” was our response. But after one summer in hot and humid Philadelphia, with 3 and 5 year old boys, and no air-conditioning, Katrina and I realized that Telluride sounded like a wonderful opportunity to escape back to real wilderness and to take a break from administrative work at Penn, for real, cutting edge, and new and fresh science, at least for a few weeks or a month. So in the summer of 1985 I agreed to hold a small workshop on “Chaos Theory and Theoretical Chemistry,” designed for those young faculty, and their students and postdocs, moving into this newly developing area: Where did things stand? What important new problems might be solved? By what methods? How should the field develop? How might different groups proceed independently working on different problems and applications, but then come together again the following summers to compare and evaluate progress in an entirely open manner? All this, hopefully leading to the foundations and establishment of a new area of theoretical chemistry. Our young boys were then also part of the first early sessions of Camp Telluride, which took them into the soaring mountains and rapids filled rivers of southern Colorado (at 9000 feet of altitude!) and (safely, we hoped!) out of the immediate hands of their parents who needed a day off, now and them. The TSRC grew and prospered far more quickly than any of us expected: from one small workshop in 1984 to five in 1988 including the first large workshop (Spectroscopy of Highly Excited States of Molecular Systems) where both theorists and experimentalists joined forces to confront a completely new set of issues in understanding the results of a whole new generation of experiments, where for first time analysis would be based not on “assignment” of individual spectral “lines” but rather on understanding “clusters” of such spectral linesa whole new concept where theorists and experimentalists worked together to develop both new methods of spectral analysis and new collaborations that then expanded over the whole world of high energy spectroscopy. Again, focusing on “what we don’t know,” and “what we don’t understand,” rather than the opposite, opened up whole new vistas and did, over several summers, lead to new and fuller, if still not entirely complete, understandings. In that same year I ended up as President of the TSRC as both Salamon and Berry were off on Sabbaticals in Europe, and by 1990 the TSRC regularly hosted six workshops, including one larger one on neural networks (this included artificial intelligence, or AI, too) organized by a completely new and independent group (not a chemist among them, and organized

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UNIVERSITY OF WASHINGTON AND NIST Oh, my! Why did Bill Reinhardt move yet again? The key, and perhaps surprising, element here turned out to be finding schooling appropriate to the needs of our complex boys. The famous Quaker Schools of the Philadelphia surroundings, rather than representing that famous aphorism of pre-Civil War America, “Friendly Persuasion,” turned out to be largely teaching to the standardized exam machines designed to produce students with high SATs and then admissions to top level Ivy League Universities. This did not suit our boys, perhaps similarly to how my early education, and that of my wife Katrina, did not take place in a very orderly fashion either. Friends in Seattle, Washington, encouraged us to take a look at their more relaxed (although also private) schools, which tended to emphasize contemplative understanding, and good social interactions, rather than rote learning with massive levels of homework even in the fourth and fifth grades. We looked and we moved. Research at UW began with extensions and continuations of earlier modes of work with S. S. Han extending work involving analytic continuation for the solution of many-particle scattering problems, and then John Hunter, III, and followed by Gordon Hogenson, Lynn Amon, and Mark Miller greatly extending the use of adiabatic switching for calculations of upper and lower bounds to free energy differences, entropies, and even absolute free energies of atomic clusters. Caren Seagraves, an always independent soul, produced beautiful work indicating that membrane proteins might have more than a single low energy folded structure. Theoretical electrochemists and senior physicists from the FSU, S. Burlatsky and A. Brodsky, joined forces with the Center for Process Analytical Chemistry, then a major operation involving both chemists and others from across the University and also from Industry, in problems of design and use of microelectrodes. However, a major new set of activities was also, almost by accident, taking shape and would dominate the later parts of my research career. As noted earlier, as a Fellow of JILA I had many colleagues from the National Institute for Standards and Technology, or NIST, both in Boulder at JILA and also at NIST’s home base in Gaithersburg, Maryland, where I’d spent a sabbatical in 1982−83. An old scientific friend, Charles W. Clark, invited me to spend a month at NIST in Gaithersburg in the Summer of 1994. Clark fully expecting that NIST would 3622

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the quantum mechanics (and the classical mechanics, too) of the correlated motion of several electrons is quite difficult to describe, the Hartree approximation utilized the idea that individual electrons move in the average (static) potential of all other electrons. Physicists refer to this same idea as a mean-f ield approximation. As for electrons, being Fermions, each is in a different one-electron orbital, the motion of all electrons had to then be determined self-consistently, by iterating to convergence, initial approximations for each of these unknown orbitals. G-P theory is in a sense the same, except only requiring determination of a single one-particle orbital for all of the identical Bosons, having started with an approximation to that single orbital, and then iterating to self-consistency. Clark’s group and others had used this iterative method, starting almost immediately following the emergence of the first BECs in 1995, but found that achieving self-consistency for Bosons in a laser trap was a long and tedious computational process. Starting from an entirely different viewpoint, using time dependent methods on coordinate space grids, and the method of Fast Fourier Transforms (FFTs), to switch back and forth between representations where the coordinates, and then the momenta, were diagonal, I found that very rapid convergence to excellent solutions of the G-P equation were generated via the same ideas of adiabatic switching as used for those upper and lower bounds to free energies in the Seattle research group. No iterations to achieve self-consistency were needed, rather simply the adiabatic turning “on” of the interparticle interaction. Thus, a more efficient method was in hand, a thing of value, but not yet producing novel or unexpected results that could not be obtained in different ways, albeit less conveniently. But it is worth noting that if an initial state, with N noninteracting particles in the same initial single particle wave state that had a fixed number of nodes, then the adiabatic turning on of the (usually repulsive) interparticle interaction normally would lead to a stationary solution of the G-P equation with precisely the same number of nodes. Thus, stationary excited states could be as easily generated as the ground state. But a second step went well beyond that. Being a novice when it came to working with Bosons, and not Fermions, I was curious about the quantum phase of a BEC. Two common uses of that phase in Bosonic systems being that of Glauber in relating electromagnetic waves of classical Maxwellian dynamics, and their quantum counter parts being a stream of photons, there being a phase-number uncertainty relation; and that of Josephson, noting that if two superconductors are weakly linked (via a Josephson junction) a current of magnitude proportional to sin(δ) can be created via a phase difference, δ, this being the difference between the quantum phases of the bulk superconductors on the opposite sides of the junction. The stationary states, described above, have a phase difference of ±π across each node (i.e., a real wave function simply changes sign at a node), and thus sin(δ) = 0, as expected for a stationary state. So now a numerical experiment was in order, and this met Clark’s command to do something for trapped BECs that hadn’t yet been thought of: Suppose one simply (numerically!) added a constant phase shift, γ, to one side of an existing phase off set of ±π across a node? What was immediately observed was the launching of a dark, density notch, soliton moving with a speed proportional to sin(γ/2), with the proportionality being the Bogoliubov sound speed in the condensate. Solitons, first observed in 1834 by Russell, as traveling water waves, are waves that propagate at a constant

soon be home to a new, and top of the line, supercomputer, and perhaps our work on computation of entropies and free energies could be expanded from the modest “model” computations we often performed in developing new methods, into large scale simulations of real, and complex, molecular fluids. Accompanied by several graduate students we had a two good summer visits, but by the end of our second visit, in 1995, it had become clear that the new NIST supercomputer initiative was not to be. But, in that same year, 1995, two groups, one at JILA and the other at MIT, had, following many years of serious efforts, worldwide, created the first gas-phase atomic Bose−Einstein condensates, or BECs. These are “mesoscopic” quantum systems, almost visible to the naked eye, of millions of atoms, trapped and sparkling in laser fields, and at temperatures down to 10−10 oK, a record low temperature at the time. Most importantly, all of the Bose condensed atoms are in exactly the same quantum state, and unlike other types of Bose condensates (such as those in superconductors), they are not hidden inside solids, but naked, visible, and malleable. So when I showed up, for a third summer of research at NIST in 1996, Clark had a rather surprising new directive for me. “Bill,” he said, “you’ve undoubtedly heard of the BEC. We now have our own BECs here at NIST, in the group of Bill Phillips,” who was soon to win the Nobel Prize in Physics for developing the trapping and laser cooling techniques that had led to the JILA and MIT production of the first actual BECs, “and,” he continued, “my group has done some good and interesting initial computational modeling of these quite novel systems.” I was puzzled, as I had no idea where this conversation might lead, as yes, I knew of the new BEC; in fact, I’d been on a search committee at JILA, during my last year there, which had hired Carl Wieman, now a BEC star and Nobelist to be, although we’d hired him to look for a possible finite dipole moment of the electron, a far removed problem in the area of precision measurements, but I had never given even a moment’s thought as to BECs being a possible area for my own research. So imagine my shock and surprise when Charles then said, “With your entirely different background in theoretical chemistry, I think you will know things that we atomic physicists are unaware of, and I hope, and expect, that by the end of the summer, you will not only have created new theoretical models of BECs, but will have used them to look into aspects of the BEC which none of the rest of us have even yet thought about!” That “!” indicating my immediate thought that this could never materialize, as I, at that moment, knew nothing at all about many-Boson systems, having spent much of a lifetime thinking only about those of many-Fermions. Electrons have an exclusion principle; Bosons do not. A world of difference. Without sticking to the precise order in which, indeed novel, approaches to the simplest reasonable description of BECs, namely use of the Gross−Pitaevskii (G-P) model, were worked out, two quite novel results were in hand by the end of that summer and then into the Fall, back in Seattle, where they became the mainstays of my ongoing research up until my retirement. Theoretical chemists, whether or not they realize it, are quite familiar with G-P theory, although they’d know it by its original name: Hartree’s Self-Consistent Field Theory of electronic structure, well-known in both theoretical chemistry and atomic physics from 1927 onward, almost 35 years before it appeared in the theory of BECs. Hartree’s idea was simple. As the motion of one electron is often simple to describe, while 3623

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important subfield,” I just followed my continuously changing interests. Greatly to my surprise, as I began to chat with former students and postdocs, from over more than a 45 year period, as retirement neared and became a reality, I heard, uniformly, that the young scholars who had chosen my mentorship did that precisely for my flexibility and that they immediately understood, in comparison to other possible choices, that I would be one to offer and encourage intellectual freedom and choice and experimentation (with both failure and success being necessary ingredients), rather than assigned work, for a pre-existing program, be it at a lab bench or computer terminal. I love my wonderful wife Katrina and our two boys James and Alexander. I still cannot spell ....

velocity but do not spread or dissipate, their wave shape being a constant in time. Experimental creation of such a phase offset, on a part of a trapped BEC, and the resulting production of a corresponding soliton at the boundary of that phase discontinuity, was soon demonstrated in the Phillips Lab at NIST. These numerical observations (first seen in 1996), followed by experimental confirmation, published in January 2000 as the millennium itself turned over, changed the direction of almost all of the research to follow, back home in Seattle, in my group at UW, as well as Physics at UW accepting me as an Adjunct Professor. There was a real lesson in persistence to be learned here before the Phillips group got going: Clark and I gave seminars, worldwide, over the three years following our computer experiments, including at NIST, about the possibility of creating such BEC solitons via shining a laser on “part of” a BEC. Experimentalists uniformly first said: “you’re crazy(!),” that cannot be done, and if it could be “there wouldn’t be a soliton in sight, as any density notches created would simply fill up.” This would be just like telling the Russell, of the famous water wave solitons, that they’d simply disperse, which is exactly what they did not do. Analytic solutions to the G-P equation, also referred to as the nonlinear Schrödinger equation, or NLSE, with “box” boundary conditions were then investigated by myself working with Charles Clark, Lincoln Carr, Mary Ann Leung, Khan Mahmud, Sarah McKagan, Heidi Perry, Bernard Deconinck, and Nathan Kutz, and their relationship to solitonic dynamics established. These analytic solutions often being expressed in terms of Jacobi elliptic functions, led to my being invited to coauthor, with mathematician Peter Walker, chapters on these Jacobi functions, and their related Jacobi theta-functions, as well as Weierstrass elliptic functions, in the newly being assembled NIST Digital Library of Mathematical Functions, or DLMF, which may be accessed at dlmf.nist.gov. Working with Joachim Brand, and for the first time in a toroidal trap, where appropriate initial phase imprinting all the way around that circle could produce either nondissipative ring currents, or with an appropriate phase discontinuity soliton-like vortices (which we nicknamed s’vortices) were found, that might propagate with, or in a contrary direction to those ring currents. Experimental validation was far slower to come here, as getting a condensate to form, and then be properly observed, in such circular traps was no easy task. The mean-field G-P, or NLSE, description of a BEC, while able to describe many aspects of observed behavior in such condensates, has severe limitations. Correlated interactions and dynamics leading to, for example, the formation of symmetry broken or entangled quantum states, need a complex and serious extension of this more elementary theory. Such states required introduction of methods, similar to those of MultiConfiguration Hartree−Fock in the theory of electronic structure, which involve the idea that the Bosons might simultaneously exist in more than a single G-P type mode. Students and postdocs Khan Mahmud, Heidi Perry, Mary Ann Leung, Cynthia Stanich, Cory Schallaci, Sarah McKagan, Doug Faust, and David Masiello pioneered and applied these ideas.

William P. Reinhardt

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AN OVERVIEW OF THE PAST My paths were just as varied and chaotic as the description of my early, and even later, life might suggest. When sternly advised to narrow and define my later research “to attain fame and greater glory, by clearly taking over a specific and 3624

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