TORSIONAL RELAXATION OF METHYL-GROUP NUCLEAR-SPIN-SYMMETRY SPECIES

The lifetime of the first excited torsional state of a hindered methyl group of E proton-spin symmetry is found to be much less than the A-species lifetime. This is explained by a symmetric hindering potential, amplitude modulated by phonons, which also accounts for the observed widths of torsional ground-state tunneling transitions. The observations invalidate Allen's model for tunneling-splitting temperature dependence. © 1979 The American Physical Society.