Professor Fessenden received his Ph.D. in physical chemistry in 1958 from Massachusetts Institute of Technology for studies in high-resolution nuclear magnetic resonance spectroscopy. During subsequent postdoctoral training at the California Institute of Technology in 1958-59, he changed his interest to electron spin resonance. In 1959 he joined the Mellon Institute and applied this technique to studies of the structures of a number of the most fundamental hydrocarbon radicals. He became professor at the time of the merger that formed Carnegie-Mellon University in 1967 and joined the Notre Dame faculty and the Radiation Laboratory in 1976.
Professor Fessenden's current interests fall in the broad area of the structure, mechanism of reaction, and kinetics of reaction of short-lived or reactive chemical species. Particular emphasis is given to free radicals that can be studied by electron spin resonance (ESR) spectroscopy, as in many instances this technique can give unequivocal identification of these interesting species. In one type of experiment, radicals are produced by continuous radiolysis of liquid solutions and the radicals are studied at their steady-state concentration. The radicals identified in this way provide information on the reaction pathways while details of their electronic and geometrical structure come from the parameters of the ESR spectrum. The ESR method is also applied in a time-resolved fashion to study the formation and disappearance kinetics of radicals produced by pulse radiolysis or laser flash photolysis. Of special interest is the phenomenon of chemically induced dynamic electron polarization, in which the populations of the spin states of the radicals are altered or even inverted by chemical reactions. (ESR emission and enhanced absorption are seen in the figure for the anion radical of fumarate.
Current work in this area involves the ESR of electrons produced by photoionization and provides insight into the mechanisms by which electrons are produced and how they react with radicals. Other time-resolved techniques used in related work include optical absorption and emission with laser photolysis (to the picosecond time scale) and pulse radiolysis. Time-resolved microwave absorption, first developed in these laboratories, measures the degree of charge separation in polar electronically excited states of molecules and determines the rates and extent of charge injection into semiconductor particles from adsorbed sensitizers.
- "Role of Nonfluorescent Twisted Intromolecular Charge Transfer State on the Photophysical Behavior of Aminophthalimide Dyes," A. Samanta and R.W. Fessenden, J. Phys. Chem., 100, 3507-3512 (1996).
- "Time-resolved resonance Raman, electron spin resonance, and ab initio molecular orbital study of the structure and proton reactivity of 4-carbamylpyridinyl radicals.," G.N.R. Tripathi, Y. Su, J. Bentley, R.W. Fessenden, and P.-Y. Jiang, J. Am. Chem. Soc. 118, 2245-56 (1996).
- "Time-Resolved ESR Study of Spin Exchange Processes in the Photoreduction of 9,12-Anthroquinone-1,5-disulfonate," D. Beckert and R.W. Fessenden, J. Phys. Chem., 100, 1622-1629 (1996).
- "Rate Constants for Charge Injection from Excited Sensitizer into SnO2, ZnO, and TiO2 Semiconductor Nanocrystallites," R.W. Fessenden and P.V. Kamat, J. Phys. Chem., 99, 12902-12906 (1995).
- Professor (Emeritus)
- Office: 223B Radiation Lab
- Phone: 574-631-5354
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