Nonresonant selective spectroscopy of intermolecular dynamics in liquid in the terahertz frequency range

A new method of non- resonant selective spectroscopy has been proposed for studying the low- frequency dynamics of molecules in liquids. It uses non- resonance two- pulse laser excitation and the registration of the ultrafast optical Kerr effect. The first pulse induces anisotropy of the medium due to the orientational response of molecules, and the second pulse excites other vibrational and rotational responses while suppressing the induced anisotropy. Theoretical calculations show that this scenario corresponds to traditional single- pulse excitation of the optical Kerr effect, which does not include the contribution from orientational anisotropy. This allows for accurate determination of the spectral characteristics of intermolecular dynamics.