Molecular oxygen spin-lattice relaxation in solutions measured by proton magnetic relaxation dispersion

Proton spin-lattice relaxation rate constants have been measured as a funct ion of magnetic field strength for water, water-glycerol solution, cyclohex ane, methanol, benzene, acetone, acetonitrile, and dimethyl sulfoxide. The magnetic relaxation dispersion is well approximated by a Lorentzian shape. The origin of the relaxation dispersion is identified with the paramagnetic contribution from molecular oxygen. In the small molecule cases studied he re, the effective correlation time for the electron-nuclear coupling may in clude contributions from both translational diffusion and the electron T-1. The electron T-1 for molecular oxygen dissolved in several solvents was fo und to be approximately 7.5 ps and nearly independent of solvent or viscosi ty. (C) 2001 Academic Press.