Diffractive-optics-based fifth-order Raman spectroscopy of ultrafast liquid dynamics

Fifth-order Raman spectroscopy has the potential to enable chemists to probe the intermolecular potential between solute and solvent in liquids. Understanding the liquid state has been a long standing goal in physical chemistry as most chemistry involves the solution phase, notably biological and most industrial processes. This new spectroscopy gives direct access to the many body potential of liquids and has the capacity to solve this problem. The difficulties surrounding the spectroscopy and a new approach involving broad-bandwidth diffractive optics are explained. The experimental results from two different phase-matching geometries are presented and discussed with the conclusion that the first uncontaminated, fifth-order homodyne signal from carbon disulfide has been measured. An analysis of the signal is presented, indicating the lack of homogeneous broadening in the intermolecular spectrum as well as proposing the source of the signal is the anharmonicity of the intermolecular potential. Future directions of the spectroscopy are proposed.