Citation | He pioneered flash photolysis electron spin resonance, to provide identification of free radicals in solution, using novel concepts and new technology. It led to the further development of 'chemically induced dynamic electron polarization' which links photophysics and photochemistry. This enabled the determination of radical singlet and triplet reaction pathways and the relaxation times of doublets and triplets, and novel studies of site exchange, electron exchange and proton exchange in transient species; the theory was also provided and methods for analysis of polarized spectra delineated. This contributed to the concept of the 'new' reaction intermediate, the 'spin correlated radical pair'. He has obtained its spectrum directly using both transient esr and other magnetic resonance methods, the latter in experiments uniquely designed for normal solution studies; novel measurements of the electron exchange interaction have resulted. He is studying the effects of low magnetic fields on chemical and biochemical reactions via this intermediate, again using an original experimental method. Previous work on double resonance and double quantum techniques in nmr had led to the determination of the relative signs of nuclear spin-spin coupling constants, but (with A.D. Buckingham) he determined the absolute sign of one of these constants (through a partial-orientation technique), and contributed significantly to oriented molecule studies in nmr. These led to the determination of the hydration structure of collagen. Other original experiments included use of quadrupole couplings in the structure determination of insoluble proteins, of relaxation measurements at two nmr frequencies to determine chain mobility and the measurement of the absolute sign of an orientation parameter from dielectric anisotropy measurements. |