J. Phys. Chem. B 1997, 101, 8627-8629
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A Career As Seen from Within Daniel Kivelson I am deeply touched by the supportive collegiality implicit in this issue of The Journal of Physical Chemistry. Were I wiser, I would not tamper with a good thing, and I would turn down the generous invitation from my delightful and distinguished colleague, Mostafa El-Sayed, to write about my professional self. But I am not so wise. My early work, including my graduate research, was in microwave spectroscopy. As a direct tool for determining molecular structure, this spectroscopy had already been exhausted, but intriguing peripheral questions remained. With Bright Wilson, my research director, I effected a first-order study of centrifugal distortion in asymmetric top molecules; this not only helped with the interpretation of rotational spectra in the precomputer era but allowed one to use centrifugal distortion effects to enrich the IR determinations of force constants. This work was highly referenced and led to my appointment at UCLA, a fortunate result that affected my life positively beyond all expectations. But the work in this field that gave me most satisfaction was a spectacularly unreferenced (and therefore uninfluential and unrecognized) series of articles with David Lide in which the barriers to internal rotation of symmetric top molecules were determined from rotational spectra; this was a hot topic, and I do not know why this work was largely overlooked. Only John Deutch, my friend and ever-fascinating colleague, complimented me on this work, and he has done so often. Years later, an impressive younger colleague, Eric Heller, paid tribute to my early spectroscopic work by telling me, with a tone of surprise, that he had run into it and it had actually been interesting. Soon after, I happened upon the beautiful ESR chemistry being carried out by Sam Weissman, and I tied my destiny to ESR, at the time a barely exploited chemical tool. I spent a summer with George Frenkel at Columbia, learning the subject from him and from my very dear friend, the late Bernice Ginsberg Segal. George set me to reading the groundbreaking paper by Kubo and Tomita, and this launched me into the correlation function game just before its explosion in the 1960s. I developed a systematic procedure for analyzing ESR line shapes, and this gave my career a boost since the method was, and is, still widely used. My principal article on the subject was selected by Current Comments as one of those most referenced. The level of theory was not fundamental, but seems to have proved useful in bridging the gap between the abstraction of fundamental theory and the experimentalist’s process of data analysis. This has been the level on which I have tried to operate, that of an experimentalist narrowly focused on specific theoretical questions. (I remain a bit sensitive to the charge that the end result is neither theory nor experiment.) Once again, it is not this best-known of my papers in the field that gave me the greatest personal satisfaction, but one written with Peter Atkins in which the spin-rotational and anisotropic broadening mechanisms were interwoven into a single theoretical framework which allowed analysis of a rather complex problem in a simple manner; I believe that we had exposed and analyzed some poorly understood physical phenomena and were not merely refining or reformulating previous knowledge. Although my early proposals were to use ESR as a probe of gaseous free radicals, in particular CH3, my consistent failure to detect this radical was happily overlooked by the NSF, that wonderfully effective and unbureaucratic creation of the welfare S1089-5647(97)01617-9 CCC: $14.00
state. (My first failure as a graduate student involved the microwave detection of the OH radical; the competition, Charles Townes and co-workers, was too strong.) Though the search for CH3 was fruitless, I had some success, working with a number of fine collaborators such as Bob Neiman (my first student), Ann Walker, and Bruce Kowert, in studying free radicals in solution. This work led me to the study of line shapes as a function of relaxation, and subsequently to the inverse study of relaxation as probed through line shapes. ESR provided great molecular relaxation data, but unfortunately these tended to be restricted to rather ugly (unsymmetrical), strongly interactive (free radical) probe-molecules in somewhat exotic solvents. This, I believe, limited the theoretical interest in these studies. Furthermore, my ESR equipment was aging, the new pulse techniques strained my experimental competence, and Jack Freed was doing similar work better. So I shifted fields. The advent of the laser made dynamic light scattering studies viable and provided a new tool for studying molecular relaxation in liquids. (Some years earlier, as a paid consultant, I had advised that, because of spontaneous emission, LASERS could not be built; my role as consultant was short-lived.) I recognized the potential of lasers for the study of relaxation, but I was also seduced, as a one-time spectroscopist, by the fact that heterodyning could yield resolutions of 1 part in 1013; this mindboggling and tantalizing possibility led me, in part, to follow an instrument rather than a science, a practice that I have always deplored. I was fortunate at the time in having Tom Keyes as a graduate student, since, among other things, he taught me much more about light scattering and its possibilities than I ever taught him. I was also fortunate in being close to John McTague, whose inherent talent for closing in on important scientific problems helped me find my way. As time went on, my interest shifted to liquids at lower and lower temperatures, from normal, or hydrodynamic, liquids to viscoelastic systems. I became a committed practitioner of the Mori-Zwanzig approach, which might be described as a molecular, generalized hydrodynamic construct. I very much liked this formalism, which is simple in concept and well suited to use by experimentalists because it projects all of the difficult (impossible?) physics into experimentally measurable parameters. Actually some years earlier, Ken Ogan, one of my students, and I developed what we thought was an elegant and systematic formulation of ESR in terms of the Mori formalism, but, sadly for us, it caused hardly a ripple. In the mid-seventies, together with Paul Madden (with whom I have had wonderful, continuing collaborations over many years), I set out to write a book designed for non theoretically oriented chemists that would enable them to use the Mori formalism in treating a wide range of relaxation phenomena on a common formal structure; we started with what we thought was the simplest of the relaxation phenomenasdielectric relaxation. Ten years later, with the book not written, we were still trying to understand dielectric relaxation, but along the way we wrote papers and a long study for AdVances in Chemical Physics which has apparently proved interesting and useful to a number of people. One of our goals, as well as that of many others, was to obtain enhanced understanding of molecular relaxation in liquids by extending the simplest models (70 years old and fantastically successful) in which a macroscopic particle is coupled to continuum hydrodynamic and dielectric baths. Paul Madden © 1997 American Chemical Society
8628 J. Phys. Chem. B, Vol. 101, No. 43, 1997 and I worked on dielectric friction, and Bob Schwartz, Donna Hoel, and I produced a reasonably popular semimacroscopic model which attempted to take partial account of the discreteness of solvent molecules, but I no longer believe that one can make serious progress by simply doctoring the continuum models. Many would disagree. I also eventually concluded, as did many others, that the simple extension of the Mori generalized hydrodynamic approach, which depends upon the introduction of more and more not-well-specified “slow” dynamical variables, could not be used to study deeply supercooled liquids because the number of such variables required becomes too large. Richard MacPhail and I examined various mode-coupling extensions of the Mori formalism, an approach that had been used so successfully by Kawasaki (whom I had the pleasure of meeting in the 1960s while we were both visiting Irwin Oppenheim at MIT) in treating critical slowing and that had recently been brilliantly developed for use with supercooled liquids by Leuthheusser, Go¨tze, and others. We concluded (and this remains an extremely controversial, even contentious point) that the modecoupling approach encompasses too small a region of the relevant Hilbert space to be applicable to supercooled liquids. One phenomenon on which our light scattering experiments had focused was the interaction of orientational and shear modes and the existence of what we called “shear-orientation modes”, and I participated with two very talented graduate students, Russ Lipeles and Daniel Ou-Yang, in developing an alternate technique, “shear-induced birefringence”, for studying this phenomenon; this was the closest I have come to being a “coinventor” of an experimental technique. A few years ago I focused my research totally on supercooled liquids as they approach the “glass transition”. I have never been as excited by my science as with this work because it represents an attempt to develop a novel, initial description of important, but still not well-understood, phenomena. The theory is much more fundamental than anything with which I had previously been involved (except perhaps for my isolated work on reactive barrier-crossing with Gilles Tarjus), and the experiments led us (Xiaolin Zhao and two undergraduates, Alice Ha and Itai Cohen) to the identification of what may be a new class of phases. Perhaps we are succeeding and perhaps we are not, but both the theoretical and experimental challenges, as well as the original level of the science, have been exhilarating, the sense of exhilaration having been enhanced by the close collaboration and friendship that I have developed with Gilles Tarjus and by the incredibly rewarding interaction with my son, Steven. As a computer-illiterate, I have been skeptical about computational science. But Mike Allen infected me with the computation(al) virus. Although unable even to log on to a serious computer, by collaborating with a number of remarkable scientists, I have become a participant in the field. I am still a skeptic, but believe that simulations are great for “educating one’s intuition”. With Mike Allen, Julian Talbot, and Daan Frenkel, and with Glenn Evans at the theoretical helm, we carried out structural and dynamic studies of hard ellipsoids which we thought could serve as model molecules, much as hard spheres have served as model atoms. Do I prefer research or teaching, I am often asked. There is no answer. Teaching at all levels is fulfilling and challenging, and at the graduate and postdoctoral level teaching and research are, of course, inseparable. To me, the highs (and lows) that come with teaching are major emotional events. The honors I have won are few, this present journal issue being among the best, but the prize that has given me the greatest pleasure is an
in-house teaching award. Perhaps this is because I regard myself as yet another adequate researcher, but a more than average teacher. My serious interest in teaching has led me to coauthor a number of idiosyncratic textbooks, none of which has received unfavorable criticism, possibly because none has been published. From time to time I have strayed slightly from basic science. In 1964, Margy and I were part of the first “Defense Science Seminar” designed by my colleague Bill McMillan to turn selected young scientists into useful Pentagon advisors. The intensive month at the seminar was, for me, a monumental, fascinating, and, at the same time, horrendous experience. Among the perks were the opportunities to spend quality time with John Balderschwieler and the late Bill Flygare and to be part of a group visiting the Naval Testing Station at China Lake that was allowed in (under guard) without proper security checks because we were too drunk for bureaucratic processing. I was awed and impressed by what I heard during that month, but grew more confirmed in my antiestablishment outlook. The Pentagon picked me up as a consultant for a year, but my fuzzyminded, peacenik tendencies were so apparent that I gave up before confusing the DOD with my wise pronouncements. While still graduate students, after having read Gods, GraVes and Scholars, which recounted the stories of great archaeological discoveries, Margy and I were bitten by the archaeology bug. That interest has enriched our lives and started us on aggressive extraprofessional traveling, tainted us with the collecting addiction, and ultimately led Margy and me to interact with members of a nonphysical science community focused on the roots of civilization. Encouraged by our sparkling friend, Jay Frierman, we tried to blend our science with history. Margy and I worked with the now renowned English archeologist Colin Renfrew on a statistical analysis of pre-Columbian tombs; at UCLA, along with Judy Swain, one of the most memorable undergraduates with whom I have had the pleasure of working, I tried to extend to ESR the thermoluminescence dating techniques of ceramics invented in large part by two exceptional, but very different, colleagues and friends, Leon Knopoff and George Kennedy. There are no significant accomplishments to validate my efforts in scientific archaeology, but I relish this segment of my professionally related life, which has continued to bring me pleasures, including friendship with the distinguished Byzantine scholar and independent spirit, the late Milton Anastos. Today my interest in noncontemporary history is kept alive by my very close and gratifying relationship, both intellectual and personal, with my Medievalist daughter, Valerie. From time to time I have tried my hand at other projects. With Kyle Bayes and Russell Tice I examined the possibilities of using cyclotron resonance in gaseous discharges to study lowenergy electron-molecule scattering; we enjoyed and learned much from this work, and I occasionally still get reprint requests, but we all lost interest in the program. Jim Dix, Jared Diamond (a true Renaissance man in his breadth of scholarship), and I studied molecular motions in phospholipid bilayers by means of ESR, the closest I have ever gotten to problems of biological interest; this work, and later related NMR studies with Bret Berner, progressed well, but we quit because we reached a point where we could not envisage a next step. Early on, following the lead of Jiri Jonas, I recognized the importance of collecting pressure data, and at a time when few were performing such measurements, Bill Plachy, and later Danny Miles, carried out ESR and light scattering measurements at pressures up to several kilobars, measurements that I believe were significant, primarily because so few of their kind had been (or still have been) related to relaxation studies.
J. Phys. Chem. B, Vol. 101, No. 43, 1997 8629 When first I came to UCLA, I looked upon Los Angeles as a cultural desert to which we had been exiled and UCLA as a provincial institution. Though I often complain about almost everything (and there are hundreds of nonrespectful extant letters that confirm this), today Los Angeles is my residence of choice and UCLA my institution of choice. My department has been an unbelievably wonderful one. One visitor commented that the physical chemists get along “disgustingly well”. The departmental character owes much to the positive leadership of Ken Trueblood, a remarkable man. For over 40 years, nearly daily, Bob Scott has taught me thermodynamics and inveighed passionately at the unrighteous in science and societysa better colleague could not be found. Howard Reiss, one of the few true geniuses in that he thinks not only faster than most of us but orthogonally (and at the same time productively), has been generous with ideas, as well as with encouragement. Chuck Knobler and Bill Gelbart have literally become mainstays of both my professional and personal life, both in their very different ways, passionate scientists and friends. It is common for department members nearing retirement to be excluded and overlooked, but I have been extraordinarily fortunate to be carried along with our explosively dynamic and collegial group of young physical chemists including Emily Carter, Jim Heath, and Andrea Liu. Students have contributed greatly; the work done by Stephen Gomperts and Massimo Noro (no longer my students but my friends) could have qualified for doctorates. Although some years ago I decided that I would not take new graduate students, the opportunity of working with Hajime Sakai was too good to let pass; this exceptional young scientist has not allowed me, fortunately, a moment of intellectual repose. I mention names because a story without names is no story. But I do not want to minimize by exclusion the collaborations and friendships with the many others who have meant much to me and whom I truly like and admire. (Of course, we have had our overintense exchanges in “the pursuit of truth,” but, I believe, collegiality and humor have almost always been preserved.) In addition, there are a few people whom I would like especially to mention because of the direct impact they have
had on my “professional” life. My life, professional and nonprofessional, has been nourished by close friends; among my closest science-friends throughout the years have been Paul Martin, Bert Malenka, and Ray Orbach, in the presence of whom I always feel intellectually stimulated and emotionally fortified. My father, Harvey Kivelson, who as an immigrant achieved, during the depths of the Great Depression, the American dream of a civil, upper middle class, cultured lifestyle for his family, and gave me unlimited encouragement and support to follow and realize my own personal dreams. My mother, Eva Kivelson, a brilliant if undisciplined intellect, a physician at a time when few women were professionals, instilled in me a passion for matters intellectual and cultural, thereby dooming me irreversibly to the effete Ivory Tower. E. Bright Wilson, Jr., as my graduate mentor, not only taught me the trade of physical chemistry but imbued me with awe and admiration for the scientific method, and he communicated his intense commitment to scientific and personal integrity; I may not have been able to perform at the level he envisaged and taught and lived, but I at least have always had appropriate pangs of guilt when I lost my way. (Of course, guilt comes easily to me because of my Jewish heritage.) Irwin Oppenheim, with whom I roomed in college and who gave meaning to my feelings of intellectual inferiority, has continued to be my teacher and closest of friends throughout the years. In recent years I have picked up a new collaborator who has affectionately and with humor led me to a new appreciation, understanding, and vision of sciencesmy son Steven. And throughout the years, over and above what she has been to me in all other aspects of life, my wife Margy has continually been part of my scientific experience, enriching it with encouragement, criticism, scholarly input, and her own deep commitment to both family and science. Although the papers that Margy and I coauthored may not be personal bests, the very process of working together has been stimulating and gratifying. Margy, Steven, and I have not yet triauthored a scientific paper, although we have written a piece on Turkoman rugs, a family obsession.
