John C. Polanyi

(b. 1929)

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(1929–) Canadian chemist

John Polanyi was the son of the distinguished physical chemist Michael Polanyi. Born in Berlin, Germany, he was educated at Manchester University and at Princeton, where he obtained his PhD in 1952. He moved soon after to Toronto University, being appointed professor of chemistry in 1962.

Beginning in the 1950s Polanyi has sought to throw light on the nature of chemical reactions. What actually happens, he asked, during the reaction H + Cl2 → HCl + Cl? The reaction was known to be strongly exothermic; it was not known, however, how this released energy was distributed in the various degrees of freedom of the reaction products. D. Herschbach had begun detailed investigations of reaction mechanics by measuring the velocities and angular distribution of the reaction products using molecular beams. In contrast Polanyi described his own method as one in which “the molecules formed in chemical reaction do the work by signaling to us their state of excitation…through infrared emission.”

Initially Polanyi and his coworkers had to work with a detector “only slightly more sensitive than the palms of our hands…a thermocouple.” They were soon able to replace this with semiconductor infrared detectors. By analyzing the infrared emission, Polanyi was able to measure how much of the reaction energy was stored as molecular vibration and rotation. In this way he was able to show that in the example cited above two distinct states of the molecule HCl were formed: one with high vibrational and rotational excitation, but low translational energy; and the less common state with low vibrational and rotational energy but high translational energy. Polanyi has continued to work in the field of reaction dynamics and has developed many new techniques and derived numerous insights into the subject. For his contributions he shared the 1986 Nobel Prize for chemistry with Herschbach and Y. T. Lee.

Polanyi's work in infrared chemical luminescence led to the development of chemical lasers by G. Pimental and J. Kaspar in 1960.

Subjects: Science and Mathematics.

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