Study of the tunneling rotations in phase II of solid CH4 with high resolution neutron spectroscopy

Abstract

High resolution incoherent neutron scattering experiments were performed to study in detail the temperature dependence and shape of the tunneling spectrum of pure and oxygen-doped CH4 in phase II. The tunnel splittings increase with decreasing temperature below 5 K, in qualitative agreement with a theoretical prediction of Yamamoto et al. A finite linewidth of the tunneling lines of several μeV was observed and is explained by inhomogeneous broadening due to the mixture of nuclear spin symmetry species. A qualitative comparison between the theoretical predictions and the experimental results is presented.