Mixed Domain IR-Hyper-Raman Four Wave Mixing Spectroscopy.

Vibrational dephasing, relaxation, and spectra are useful probes of local environments in complex chemical systems. Here, we present the use of an infrared-hyper-Raman four-wave mixing spectroscopy, hyper difference frequency generation (HDFG) spectroscopy, as a method to resolve vibrational dephasing and spectra in the bulk. Coherent vibrations of dichloromethane and cyanocobalamin are resolved in both frequency and time. Tuning the two-photon interaction frequency toward an electronic resonance in cyanocobalamin enhances the vibrational signal, demonstrating electronic resonance enhancement through electron-vibration coupling mechanisms in cyanocobalamin. This work motivates use of mixed-domain HDFG to measure coherent vibrational spectra in both frequency and time and to extract electron-vibration coupling information in molecular systems.