Terahertz vibrational modes induced by heterogeneous nucleation in n-alkanes

► We describe the observation of a broad and strongly temperature-dependent peak in the terahertz absorption spectrum of several linear n-alkanes. ► On cooling from the liquid into the rotator phase, the absorption is enhanced within a very narrow temperature range at the temperature of the first-order phase transition. ► This peak is associated with an enhancement in the vibrational density of states, induced by the heterogeneous nucleation of the rotator phase from the liquid.