Nowadays, chemical kinetics of gas phase and gas-surface reactions has access to intimate molecular dynamics of individual reactive collisions. Here I’ll revisit some episodes from its infancy. About 60 years ago, only a few chemists were seeking means to observe molecular reaction dynamics. Some somber chemists dismissed the prospect of “single-collision” chemistry as “a lunatic fringe.” My entry to the fringe came as a first-year graduate student in 1955 at Stanford, in a physics course. The professor, Walter Meyerhof, made a brief digression to mention Otto Stern’s 1919 experiment using a molecular beam to test the Maxwell-Boltzmann velocity distribution. For me, it was love at first sight. Crossed beams ought to be an unequivocal way to confirm a reaction is elementary and to study directly its dynamical properties. My mentor, Harold Johnston, had imbued me with his passion for kinetics and a sense for historical imperative. From him I’d learned about the reactions of alkali atoms with halogen containing molecules, explored in the 1920s by Michael Polanyi, who found some had unusually high yields of alkali halide products. In 1960, I was an assistant professor at Berkeley, with two students. We carried out crossed beam experiments with simple apparatus adequate for facile alkali reactions. The sought after dynamical bounty was attained, the first observation of angular and velocity distributions of reaction products. Moreover, we had the pleasure of showing the results to Otto Stern (1888-1969) himself; he had retired to Berkeley. Soon after, Michael Polanyi (1891-1976) also visited Berkeley. Much more was to come. Historical destiny is intriguing. E.g., Meyerhof had to emigrate in the Nazi era. Otherwise, very likely he would not have been in a Stanford classroom, captivating a susceptible student.

Emergence of molecular reaction dynamics

255th National Meeting (2018)

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