Liquid state torsional dynamics of butane: The Kramers rate and the torsion angle correlation times

The diffusion equation for hindered internal rotation of a butane molecule in the liquid state is solved for the Kramers-like rate for trans–gauche isomerization and the torsion angle correlation times. High accuracy solutions obtained by numerical quadrature and approximate asymptotic results are compared with previous molecular dynamics calculations of butane in several thermodynamic states.