Double-Minimum Potentials in Hydrogen-Bonded Solids

Abstract

Using a simple one‐dimensional model of H bonds, vibrational‐energy eigenvalues, eigenfunctions, transition moments, and absorption intensities are calculated for a series of symmetric and asymmetric double‐minimum (D.M.) potentials. On the basis of the results obtained, the necessary requirements for observing doublets in the infrared spectra of H‐bonded solids are given. In most cases an asymmetric D.M. potential does not give rise to such doublets. Attention is drawn to the rapid ``switch‐over'' from even‐odd, odd‐even to ``left‐left,'' ``right‐right'' selection rules when a slight asymmetry is introduced into a symmetric D.M. potential. Also, a very rapid uncoupling of resonance interaction between accidentally coincident ``left'' and ``right'' levels of strongly asymmetric D.M. potentials is predicted. The importance of obtaining accurate relative intensity values and of determining the infrared and Raman spectra of both the H‐bonded solids and their deuterated analogs at several temperatures is emphasized.