Spin isomer conversion and orientational ordering in solid methane: II. The second moment

Abstract

The various contributions to the second moment in methane, CH4, are investigated. A general expression for the intermolecular second moment is obtained. Using this, the intramolecular second moment was measured using a series of observations during spin isomer conversion. The value found, near 1.5 G2, suggests restricted motion of a preferred axis of reorientation. A search for the onset of the intramolecular second moment shows that it occurs in the same region as the onset of birefringence.