Comparison of different methods for calculating the paramagnetic relaxation enhancement of nuclear spins as a function of the magnetic field
2008 (English)In: Journal of Chemical Physics, Vol. 128, 052315- p.Article in journal (Refereed) Published
The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion (known as the paramagnetic relaxation enhancement, PRE) arises primarily through the dipole-dipole (DD) interaction between the nuclear spins and the electron spins. In solution, the DD interaction is modulated mostly by reorientation of the nuclear spin-electron spin axis and by electron spin relaxation. Calculations of the PRE are in a general complicated, mainly because the electron spin interacts so strongly with the other degrees of freedom that its relaxation cannot be described by second-order perturbation theory, or the Redfield theory. Three approaches to resolve this problem exist in the literature: the so-called slow-motion theory, originating from Swedish groups, and two different methods based on simulations of the dynamics of electron spin in time domain, developed in Grenoble and Ann Arbor, respectively. In this paper, we report a numerical comparison of the three methods for a large variety of parameter sets, meant to correspond to large and small complexes of gadolinium(III) and of nickel(II). It is found that the agreement between the Swedish and the Grenoble approaches is very good for practically all parameter sets, while the predictions of the Ann Arbor model are similar in a number of the calculations but deviate significantly in others, reflecting in part differences in the treatment of electron spin relaxation. The origins of the discrepancies are discussed briefly.
Place, publisher, year, edition, pages
2008. Vol. 128, 052315- p.
NMR, paramagnetic relaxation enhancement, relaxation dispersion, proton T1, theoretical models
IdentifiersURN: urn:nbn:se:su:diva-15145ISI: 000253125700029OAI: oai:DiVA.org:su-15145DiVA: diva2:181665