Nuclear Quadrupole and Magnetic Resonance Study of Molecular Motion in Solid HCl and DCl

Abstract

Nuclear magnetic and quadrupole resonances were used to study the structure of hydrogen and deuterium chlorides below and above the transition points. The chlorine pure quadrupole resonance frequencies were measured between 20°K and the transition points, showing that a single molecular libration frequency does not fully account for the temperature dependence probably because of the effect of intermolecular hydrogen bonds. The structure of the high temperature phase was proposed as being a hindered rotational one, on the basis of the second moment of the proton magnetic resonance and of the direct observation of chlorine magnetic resonance, the latter leading to the activation energy of 0.7 kcal/mole for rotation. The self-diffusion of molecules below the melting point causes further narrowing of proton resonance line above 130°K, with an activation energy of 5.6 kcal/mole.