Trans–gauche energy difference from Raman spectrum of gaseous pentane

The trans–gauche energy difference derived from the Raman spectrum of gaseous pentane is rediscussed for the case when the explicit temperature dependence is not available. In that case differences in Raman scattering cross-section and degeneracy of the conformational energy levels needs to be taken into account. Using ab initio derived Raman cross-sections, a good value for the trans–gauche energy difference is obtained. This method can be applied to systems which do not allow for study over a wide temperature range such as polymers.