© Copyright 1996 by the American Chemical Society
VOLUME 100, NUMBER 19, MAY 9, 1996
Photograph by Thomas C. LaVergne
James Lloyd Kinsey
Introduction As our cover piece shows, James Lloyd Kinsey is the person who made us all equally confortable in the time as in the frequency domains. Armed with the deep respect for spectroscopy that he acquired while getting his Ph.D. with Bob Curl at Rice and with the understanding of dynamics that he developed as an early member of the Berkeley lunatics group of Dudley Herschbach, he set on a course to combine the two. His mission was to view dynamics as structures unfolding in time by looking for the kind of observables that will provide the detailed and precise information that one is familiar with in spectroscopy. In this he was also influenced by Dick Bernstein’s view of the S0022-3654(96)03468-5 CCC: $12.00
continuum as an extension of the bound region of the potential. Dick was however, thinking in terms of stationary states, while what Jim wanted was to view the scattering act as an extension of the spectroscopy of states just below the dissociation limit. As it ultimately turned out, this view was highly productive not only for dynamics but also for spectroscopy. There is another characterization of Jim’s work: a methodological one. Jim (probably unconsciously) sought to bring to chemical physics the “scientific method” as we teach it and, on good occasions, also practice it in physics. His approach was always to clearly identify a theoretical issue and to design and © 1996 American Chemical Society
7736 J. Phys. Chem., Vol. 100, No. 19, 1996 carry out an experiment that would address it. We can speculate that his deep familiarity with that most orderly topic, the coupling of angular momenta, led him to seek the same clarity and precision in other areas of science. One finds all the elements of the mature JKL approach already in his first full-fledged attempt. As far as one can tell, Jim saw the early infrared chemiluminescence experiments of John Polanyi as providing the degree of detail that he was after. Here was a spectroscopic kind of information coming from a dynamics experiment. While on sabbatical in Wisconsin, he quantified what he considered one was learning from such measurements. As one of the early practitioners of Dick Zare’s laser-induced fluorescence (LIF) technique for exploring quantum state distributions of reaction products, Jim sought to obtain not only the final internal state distribution but also the scattering information, which is the distribution of final momenta. His 1977 paper on “Fourier Transform Doppler Spectroscopy” demonstrated a method by which an arbitrary velocity distribution in 3D could be obtained from sub-Doppler spectroscopic measurements. (Jim’s tendency to Fourier transform anything that comes his way paid its early dividends in that instance.) Although the full-blown method has only seldom been realized, it provided a framework for many subsequent variants on the Doppler theme. It was however still short of what Jim really was looking for. The “unfolding in time” was not yet there. It was a 1981 Gordon conference talk by Rick Heller that provided for him the missing link. At that time, at MIT, his student Dan Imre was already looking into the spectroscopy of ozone in the Hartley band. What Dan had was lots of “fluorescence” signal. Upon his return to Boston, Jim had decided to try to watch the molecule in the process of falling apart (or what the scattering types call a “half-collision”). It turned out that the signal was sufficient for the purpose. By dispersing the emission in a spectrometer, Dan and Jim could tell that ozone was dissociating essentially without bending. The signature was very clear: there was no emission into the bending states of the (electronically) ground state molecule. For the first time chemists have literally watched how a system evolves along its reaction coordinate. Methyl iodide showed that complementary information can also be obtained. You would think that during the dissociation the C-I bond will extend, and the spectrum showed this very clearly, but it was not obvious that somewhat later the CH3 umbrella motion will light up, and it did. A good chemist will say that the CH3 group needs to become planar, but the experiment (see front cover) told that planarity is delayed until
after the C-I bond has stretched significantly. Iodobenzene was a foray into the world of larger molecules, where one could clearly see how the many vibrational modes organized themselves into the few that constitute the chromophore and the many others that are the “bath”. All that time Jim remembered that the dissociation threshold is not really a sharp transition. If molecules will emit while falling apart, molecules can also be made to emit into states below the dissociation. Together with Bob Field they developed stimulated emission pumping (SEP), which has become such a central tool for the study of the spectroscopy and dynamics of energy rich molecules. Like other great experimentalists, Jim is really a “closet theorist”, except that he comes out somewhat more often than others and about a quarter of his papers are theoretical. The program his Mac sees most often is Mathematica, and at this point it does not even need to be opened for his Mac to be able to do 6 j symbols. (It is still not so good on the 9 j ones.) Other restrictions due to symmetry and, in particular, their implications for the density of states and for selection rules, time correlation functions and their application to the time domain formulation of spectroscopy, and the maximum entropy formalism are only some of his interests. Jim’s longtime interest in large amplitude motions in anharmonic systems led him to being the first to look for chaos in molecules using real data. The strong coupling of theory and experiment is also evident in the secret door that leads from his office as Dean of Natural Science at Rice University directly into the lab. While everybody recognizes the leadership that he provides as Dean, Carter Kittrell and Bruce Johnson, who head the team on the other side of that door, will tell you that Jim is always ready to interrupt for scientific discussions. The first paper of this special issue is but one outcome of this fruitful collaboration. While doing all of the above, Jim never ceased to be a devoted husband and father, a caring mentor for his students, a pivotal citizen of his department, and a gracious host to his visitors. Many of us think of him not only as a source of inspiration but equally as somebody to whom you come for advice, particularly so when you really need it. Eric J. Heller Paul L. Houston Raphael D. Levine Ahmed H. Zewail JP963468Q
