Coherent multidimensional vibrational spectroscopy

Coherent multidimensional vibrational spectroscopy (CMDVS) is an emerging field that offers new oportunities to probe specifically intramolecular and intermolecular interactions in complex samples with the improved resolution and selectivity expected of a multidimensional method. In particular, it provides structural and dynamical information about correlations between modes. It provides this information on the picosecond time scales characteristic of vibrational dephasing. CMDVS is based on the perturbations that are induced in a mode when other coupled modes are excited. It is the vibrational analogue to multidimensional nucler magnetic resonance (NMR). In this review, we present the background that led to the development of CMDVS, a brief summary of the different methods of non-linear laser spectroscopy and how they can achieve CMDVS, the relationships between CMDVS and multidimensional NMR, and the theory necessary to understand the experimental results. The experimental approaches reviewed fall into three main classes: non-degenerate four-wave mixing which is doubly vibrationally enhanced, degenerate four-wave mixing which is triply vibrationally enhanced and six-wave mixing which has three Raman transitions. CMDVS has been implemented in both the time domain and the frequency domain. Finally, the review describes possible extensions of CMDVS and speculates on its future.