Hindered rotation at 2°K of the NO 2 impurity in KCl

Abstract

The electron spin resonance of the NO 2 molecule incorporated as an impurity in KCl is studied in the temperature range 1.6–10°K and as a function of applied uniaxial stress at 1.8 and 4.2°K. The results are interpreted in terms of a model in which the molecule is assumed to be in uniaxial hindered rotation, with the first excitation energy, or tunneling splitting, estimated to be about 3 cm −1, to be compared with a free rotational excitation energy of 8 cm −1. Because the hindering potential is only moderate, it is necessary to include the effect of the molecular spin-rotational coupling in developing a satisfactory spin Hamiltonian to describe this system.