Biographical Memoirs Volume 90 (2009) / Chapter Skim
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GEORGE CLAUDE PIMENTEL
GEORGE CLAUDE PIMENTEL
Pages 274-305
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The information he obtained on marginal species, on chemical reactions, and on photochemical processes is a key part of the base upon which our understanding of chemical reactions and molecular structure is founded. His fearless 275
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. Few had the courage to copy the spinning grating and fast detectors of his rapid scan infrared spectrometer that extended flash photolysis into the infrared and yielded the reaction kinetics and vibrational spectra of free radicals as well as the discovery of the first chemical lasers (1964,1; 1965,1,2)
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Pimentel's CHEM Study text (1960,3) introduced a generation of Americans to the excitement of work in science as well as to the basic facts of chemistry.
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George Pimentel was born to French parents near Fresno, in central California. His family moved during the depression to a poor section of Los Angeles, where his parents separated.
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In 1946 he returned to Berkeley for graduate work in infrared spectroscopy with Kenneth Pitzer. Upon earning his Ph.D.
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INFRARED SPECTROSCOPY, HYDROGEN BONDING, FREE RADICALS, AND MATRIX ISOLATION Pimentel's publications from his graduate work and his first years on the Berkeley faculty were primarily on the infrared spectroscopy of gases, solutions, and crystals of boranes and hydrocarbons, especially cyclic hydrocarbons. His lifelong interest in unusual chemical bonding is apparent in his first few years on the Berkeley faculty.
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. Today the infrared spectra of hundreds of free radicals and transient molecules are known through the application of the matrix isolation technique and probably more than three-quarters of these were detected in the Berkeley laboratories or by former Pimentel students.
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282 BIOGRAPHICAL MEMOIRS TABLE 1 Species Observed by Matrix Isolation Molecule Reference HNO Brown and Pimentel, 1958 HCO 1960,1 N (thermoluminescence) Brocklehurst and Pimentel, 1962 O=C=N H+O Milligan et al., 1962 KrF2 1963 N2H2 Rosengren and Pimentel, 1965 NH Rosengren and Pimentel, 1965 LiON Andrews and Pimentel, 1966 FO2 Spratley et al., 1966; Noble and Pimentel, 1966 CH3 Andrews and Pimentel, 1967b CH3LiCl Tan and Pimentel, 1968 Cl-ClO Rochkind and Pimentel, 1967 (ClO)
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. George was working intensely on the CHEM Study text for high schools (1960,3)
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Parties at home around the pool in summer and during the Christmas break were a regular part of all of George's years in Berkeley. THE CHEM STUDY PROJECT In 1960 the CHEM Study project (1960,3)
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Treasury and the entire cost of the CHEM Study project was repaid one and a half times. Pimentel understood the need for a high school chemistry course that would draw people into careers in science and engineering.
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, a summer National Science Foundation program for middle school science teachers, which he had encouraged a local high school physics teacher, Penny Moore, to create. They involved leading Berkeley chemistry, physics, geology, and biology faculty members to enhance the science backgrounds of middle school teachers from all parts of the United States.
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RAPID SCAN INFRARED SPECTROSCOPY In 1961 Pimentel set out to do rapid scanning infrared spectroscopy to study the spectra and kinetics of free radicals. Together with his student K
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THE CHEMICAL LASER With this rapid scan spectrometer Kasper and Pimentel discovered IR light pulses from the first chemical lasers, the iodine photodissociation laser (1964,1) and the HCl chemical laser (1965,2)
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Since that time Pimentel led the chemical laser field with the development of new lasers and with their application to research on reaction dynamics. The emphasis was on the discovery of chemical lasers based upon new types of reactions and on the development of methods by which kinetic information could be extracted from the laser performance.
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It suggests the possibility of controlling chemical reactions through selective excitation of reagent energy states. In 1966, while the chemical laser work was progressing rapidly, Pimentel was elected to the National Academy of Sciences and in 1968 to the American Academy of Arts and Sciences.
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INFRARED EXPLORATION OF MARS The infrared spectroscopic technique furnishes the most definitive analytical technique available for remote determination of the composition of the Martian atmosphere. To conduct such measurements within the space, weight, and power constraints presented to spacecraft instrumentation and at the low light intensities available at Mars required, in 1969, an entirely new instrument design.
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With the best geographical resolution yet available, the spectrometer displayed surface altitudes varying by 8 kilometers and carbon dioxide surface pressures varying from 3.7 mbars to 8.1 mbars. The most spectacular terrain feature discovered was undoubtedly the region called Hellas, which was found to be a deep depression 1700 kilometers wide and dropping 5.5 kilometers from its rims (1970,2)
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. Pimentel served on National Academy of Sciences' committees including the Panel on Atmospheric Chemistry (19751977)
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. Committee member Alan Schriesheim, formerly vice president for research at Exxon and at the time director of Argonne National Laboratory, commented9 that there was a real effort to involve the various segments of the chemistry community -- the academic, industry, and government sectors -- and then, within these sectors, the various disciplines of chemistry -- physical chemistry, organic chemistry, biochemistry, and the rest.
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Notwithstanding his extensive public service, Pimentel vigorously continued his exploration of chemical reactivity through matrix experiments, chemical laser studies, and with new ventures into organometallic chemistry (Weiller et al., 1989) , and photochemistry on metal surfaces (1988)
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He was active to the very end, and his energy and enthusiasm and enjoyment of sports characterized his approach to life. He chose his own epitaph: "He went to the ball park every day and he let them know he came to play." i am most grateful to George's daughters, Chris, Jan, and Tess; to his wife, Jeanne; to his research students, Lester Andrews, John Baldeschweiler, Ted Becker, Bill Klemperer, and Geri Richmond; and to Jane Scheiber in the University of California chemistry dean's office for valuable additions and corrections to this memoir.
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1967b. Infrared spectrum of methyl radical in solid argon.
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1971. Hydrogen di bromide radical: Infrared detection through the matrix isolation technique.
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1967. Investigations of free radical reactions with rapid scan infrared spectroscopy: Flash noise as a limiting factor.
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1970. Reaction rate of trifluoromethyl radicals by rapid scan infrared spectroscopy.
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1957. Infrared studies of hydrogen bonding of methanol by the matrix isolation technique.
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Infrared studies of hydrogen bonding of water by the matrix isolation technique.
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Vibrational energy distribution in the di chloroethylene photoelimination chemical lasers.
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Photochemical reactions of cis- and trans-1, 2 dichloroethene adsorbed on Pd(111)
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G eorge C laude P imentel 305
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