Separating Vibrational Coherences in Ground/Excited Electronic States of Solvent/Solute Following Non‐Resonant/Resonant Impulsive Excitation

Abstract

AbstractIn a quest to track down the origin of coherent vibrational motions observed in femtosecond pump‐probe transients, whether they arise from ground/excited electronic state of solute or are contributed by the solvent, we demonstrate a method for extricating vibrations under resonant and non‐resonant impulsive excitations using a diatomic solute in condensed phase (iodine in carbon tetrachloride) with aid of spectral dispersion of the chirped broadband probe. Most importantly, we show how a sum over intensities for a select region of detection wavelengths and Fourier transform of data over select temporal window untwine contributions from vibrational modes of different origins. Thus, in a single pump‐probe experiment, vibrational features specific to solute as well as solvent are disentangled that are otherwise spectrally overlapping and are non‐separable in conventional (spontaneous/stimulated) Raman spectroscopy employing narrowband excitation. We envision wide‐ranging applications of this method to unveil vibrational features in complex molecular systems.