Infrared Matrix-Isolation Studies of Nuclear-Spin-Species Conversion

Publisher Website
Google Scholar
Abstract
Studies of the time evolution of intensities in the fine structure of infrared bands of CH3D, H2O, and NH3 isolated in rare‐gas matrices in the temperature region 6.5°–20°K have been made. The molecule CH3D exhibits a fine structure at 6.5°K with time‐dependent intensities. The data are interpreted in terms of nuclear‐spin‐species conversion. Because of rapid reconversion at 20°K it is concluded that CH3D cannot be obtained at room temperature with a nonequilibrium distribution of spin isomers by low‐temperature equilibration. The time dependence of the fine structure of the H2O bending mode at 6.5°K has been reinvestigated. The essence of the previous work is confirmed. The rate of nuclear‐spin conversion is found to be rapid at 30°K. The fine structure of the NH3 umbrella motion exhibits a time dependence which indicates that most of the fine structure observed is not due to rotation.