Relations between Raman Spectroscopy and Nuclear Spin Relaxation

Abstract

Raman spectra and nuclear spin relaxation experiments are both affected by molecular rotation. The information about molecular reorientation furnished by these experiments is shown to be related under certain assumptions, most important of which are the following: (1) The substance is a molecular liquid or gas. (2) The molecules have either linear, symmetric-top, or spherical-top symmetry. (3) The spin relaxation is controlled by the intramolecular electric-quadrupole interaction or intramolecular nuclear magnetic dipole interactions. The relations are independent of the usual crude dynamical models for molecular reorientation, and hold for both classical and quantum systems. For liquid nitrogen, the Raman and spin relaxation experiments are shown to be in satisfactory agreement. Raman experiments should be of value in interpreting spin relaxation experiments in simple molecules, since Fourier transformation of a Raman spectrum furnishes the detailed time dependence of a rotational correlation function, whereas spin experiments observe only the area under such a correlation function.