Molecular Rotation and <i>Ortho—Para</i> Nuclear Spin Conversion of Water Suspended in Solid Ar, Kr, and Xe

Abstract

Additional data supporting the nearly free rotation of the water molecule trapped in a rare-gas lattice are presented. Ortho—para spin conversion is strongly induced by adding O2 to the matrix. A simple model is suggested which correlates the intensities observed for H2O, HDO, and D2O suspended in Ar, and which estimates the rate of nuclear spin conversion to within a factor of 5 or 10. The majority of the water molecules occupy substitutional sites in the lattice obtained by removing a single rare-gas atom. Several sharp, intense lines are tentatively assigned to the H bonded OD stretch of HDO and D2O dimers in Ar. They contrast markedly with the corresponding broad band of the OH stretch.