title: Molecular properties determined from the relaxation of long-lived spin states.
abstract: The populations of long-lived spin states, in particular, populations of singlet states that are comprised of antisymmetric combinations of product states, |alpha(I)beta(S)> - |beta(I)alpha(S)>, are characterized by very long lifetimes because the dipole-dipole interaction between the two "active" spins I and S that are involved in such states is inoperative as a relaxation mechanism. The relaxation rate constants of long-lived (singlet) states are therefore determined by the chemical shift anisotropy (CSA) of the active spins and by dipole-dipole interactions with passive spins. For a pair of coupled spins, the singlet-state relaxation rate constants strongly depend on the magnitudes and orientations of the CSA tensors. The relaxation properties of long-lived states therefore reveal new information about molecular symmetry and structure and about spectral density functions that characterize the dynamic behavior.
authors.affiliation: Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Batochime, 1015 Lausanne, Switzerland.
authors.forename: Puneet
authors.initials: P
authors.lastname: Ahuja
authors.forename: Riddhiman
authors.initials: R
authors.lastname: Sarkar
authors.forename: Paul R
authors.initials: PR
authors.lastname: Vasos
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Bodenhausen