title: Cross relaxation in nitroxide spin labels.
abstract: Cross relaxation, and mI-dependence of the intrinsic electron spin-lattice relaxation rate We, are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of14N- and15N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate Weis mI-dependent.
authors.affiliation: Max-Planck-Institut für biophysikalische Chemie, 37070 Göttingen, Germany; University of Southern Denmark, MEMPHYS-Centre for Biomembrane Physics, Campusvej 55, 5230 Odense M, Denmark. Electronic address: dmarsh@gwdg.de.
authors.forename: Derek
authors.initials: D
authors.lastname: Marsh
keywords: ELDOR; EPR; Progressive saturation; Saturation recovery; Spin-lattice relaxation