George Wilse Robinson, Robert A. Welch Professor of Chemistry and Joint Professor of Physics at Texas Tech University, died from a stroke on 7 September 2000 in Lubbock, Texas. Through innovative experiments and insightful theory, Wilse and his coworkers brought fundamental understanding to some of the most important problems in molecular structure, electronic energy relaxation in molecules, crystal spectroscopy, reaction dynamics in liquids, and, more recently, the structure and properties of liquid water.

Born in Kansas City, Missouri, on 27 July 1924, Wilse attended schools in Kansas City and Clearwater, Florida. After serving in the US Navy during World War II, he enrolled at the Georgia Institute of Technology, where he earned a BS in 1947 and an MS in 1949, both in chemistry. He received his PhD in physical chemistry at the University of Iowa in 1952.

In 1954, after two years as a research fellow at the University of Rochester, Wilse received his first faculty appointment—an assistant professor of chemistry at the Johns Hopkins University. At Hopkins, he was the first to successfully develop techniques for detecting electronic spectra of isolated molecules and free radicals trapped in crystalline inert gases at liquid helium temperature.

Wilse joined Caltech as an associate professor of chemistry in 1959. Two years later, he was promoted to professor. The Caltech years were highlighted by landmark theoretical and experimental work on radiationless loss of excited-state electronic energy in molecular aggregates. The 1962 and 1963 Journal of Chemical Physics articles by Wilse and Peter Frosch are considered to be key papers in radiationless transition theory. This work, for which Wilse is widely known, continues to have a profound impact not only in photochemistry and photobiology, but in other fields as well.

Wilse and his group at Caltech developed experimental and conceptual techniques to examine triplet states, excitation energy transfer and photosynthesis, and exciton phenomena in organic crystals and biological systems. Wilse used molecular dynamics (MD) simulations to study the structure and dynamics of argon clusters. The two papers from this work are still heavily cited in the field of vapor-phase homogeneous nucleation. Wilse also was one of the first chemists at Caltech to use lasers in his research.

Wilse left Caltech in 1975 to become chairman of the physical chemistry department at the University of Melbourne in Australia. His group there was one of the first university groups to publish papers in the emerging field of picosecond spectroscopy.

In 1976, Wilse took the position of Robert A. Welch Professor at Texas Tech University, where he continued the use of picosecond spectroscopy to study liquid-state problems, including the hydrated proton and electron. He began to rely heavily on MD simulations to solve a variety of problems, including salt solutions, isomerization reactions, and liquids in high-electric fields, and in confined geometries, such as between parallel plates. In addition to MD simulations, Wilse and his research group developed analytical models to understand chemical reactions such as isomerization in liquids. In a Physical Review Letters article in 1992, the group demonstrated that the rate of activated barrier crossing obeys certain scaling laws.

For nearly two decades, Wilse endeavored to understand the most important liquid known to humankind: water. To quote Caltech’s eminent inorganic chemist, Harry Gray, “When the dust settles, and someday it surely will, Wilse Robinson will be recognized as the scientist whose work led to a fundamental understanding of the properties of this amazing substance.” Wilse’s most important contribution to the study of water was a two-state model that explains its anomalous properties, including the famous density maximum at 4°C. Using this model, Wilse and his group showed that this anomaly, as well as other properties of water, arises from outer-neighbor structural transformations.

In a 1996 Physical Review Letters article, he showed that a simple one-dimensional analytical model could reproduce the density maximum. No other current model is able to reproduce the density and other properties of water over a wide range of temperatures and pressures. In a 1999 Biophysical Journal article, Wilse showed that the curvature in the total free-energy function for protein unfolding can be attributed to the steep change with temperature of the proportions of ice-Ih–type and ice-II–type bonding in the liquid. This behavior, which leads to cold and heat denaturation, had never before been explained.

Although he was diagnosed with cancer in the spring of 2000, Wilse continued to lead his research group until he entered the hospital. He also gave an oral presentation at the Gordon Research Conference on Water in New Hampshire. After the meeting, he said that it was the best presentation on water that he ever gave. Sadly, it was also his last.

Wilse loved doing science and passionately tackled each problem. He held high scientific standards: In most of his scientific advances, he strove first to obtain a physical understanding of the problem. He also trained numerous students and postdoctoral coworkers, many of whom have become outstanding researchers in physical chemistry and chemical physics. He was not afraid to propose ideas that differed from the mainstream thought. However, more often than not, he was ahead of the rest in terms of understanding a problem. With his death, the scientific community has lost a great member.

George Wilse Robinson