George C. Pimentel

George Claude George_Pimentel(May 2, 1922 – June 18, 1989) was the inventor of the chemical laser. He also developed the modern technique of matrix isolation in low-temperature chemistry. In theoretical chemistry, he proposed the three-centre four-electron bond which is now accepted as the best simple model of hypervalent molecules.

George Pimentel’s research has had a profound effect on chemistry. The common thread of his research was a desire to understand unusual chemical bonding situations and their consequences for structure and chemical reactivity. 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 approach to exploiting new technology and developing new techniques led to pioneering work in hydrogen bonding and in the structure, bonding, and reactivity of free radicals and other highly reactive molecules, to the creation of chemical lasers, and to the infrared spectroscopy of the atmosphere and surface of Mars. 

Pimentel pioneered the spectroscopy of molecules in solid rare gases and other inert matrices beginning in 1954. He observed the first spectra of several free radicals and of many species with unusual bonding. He has provided examples of selectivity for chemical reactions in matrices initiated by infrared excitation of single normal modes.

An alumnus of University of California, Los Angeles (B.S. 1943) and University of California, Berkeley (Ph.D. 1949), Pimentel began teaching at Berkeley in 1949, where he remained until his death in 1989.

In addition to the William Procter Prize, Pimentel received the Wolf Prize in Chemistry (1982), a National Medal of Science (1985), the Franklin Medal (1985), the Welch Award (1986) and the Priestley Medal (1989).