H-1 NMRD PROFILE AND ESR LINESHAPE CALCULATION FOR AN ISOTROPIC ELECTRON-SPIN SYSTEM WITH S=7 2 - A GENERALIZED MODIFIED SOLOMON-BLOEMBERGEN-MORGAN THEORY FOR NONEXTREME-NARROWING CONDITIONS/
E. Strandberg et Po. Westlund, H-1 NMRD PROFILE AND ESR LINESHAPE CALCULATION FOR AN ISOTROPIC ELECTRON-SPIN SYSTEM WITH S=7 2 - A GENERALIZED MODIFIED SOLOMON-BLOEMBERGEN-MORGAN THEORY FOR NONEXTREME-NARROWING CONDITIONS/, Journal of magnetic resonance. Series A, 122(2), 1996, pp. 179-191
A generalization of the modified Solomon-Bloembergen-Morgan (MSBM) the
ory is presented for electron-spin quantum number S = 7/2 taking multi
exponential electron-spin relaxation into account. The theoretical app
roach closely follows P.-O. Westlund [Mol. Phys. 85, 1165-1178 (1995)]
. In the nonextreme-narrowing regime for the electron spin system, thr
ee correction terms to the traditional MSBM equations arise. They are
all derived in closed analytical form to give the generalized equation
s in a simple and convenient form: MSBM x (1 + correction). The ESR li
neshape function for S = 7/2 is also given in closed analytical form.
A number of proton T-1 NMRD profiles representing different Gd(III) co
mplexes are investigated, using a spectral density function of the tra
nsient ZFS interaction which allows for two relaxation times. For Gd-m
acromolecular complexes the largest deviation from the traditional MSB
M theory may be about 15.2%, but for the parameter sets investigated t
he corrections were about 2-3%. A computer program is developed which
calculates the NMRD profile and the ESR lineshape (X band or Q band) f
or the set of model parameters. These parameters describe the electron
spin system in terms of Delta, (the root-mean-square value of the tra
nsient ZFS interaction) and tau(v1), tau(v2), and S-0 (correlation tim
es and an order parameter of the transient ZFS correlation function).
For the paramagnetically enhanced nuclear (I = 1/2) spin relaxation, t
he parameters tau(R) (the reorientational correlation time), q (the nu
mber of fast exchanging water molecules in the first hydration shell),
and r(1S) (the point spin-dipole distance) are also used. (C) 1996 ac
ademic Press, Inc.