Triply Vibrationally Enhanced Four-Wave Mixing spectroscopy

Triply Vibrationally Enhanced Four-Wave Mixing (TRIVE FWM) is a coherent multidimensional spectroscopic technique developed in the Wright Group at the University of Wisconsin -- Madison. It is uses three ultrafast excitation pulses to excite three resonant infrared transitions in order to probe the vibrational modes of molecules both spectrally and temporally. The characteristics of TRIVE FWM spectral and temporal data were investigated using the rhodium(I) dicarbonyl acetlyacetonate (RDC) model system. RDC served as an ideal model system because its carbonyl stretching modes are spectrally resolved and provide strong signal due to their strong transition dipoles. The TRIVE FWM technique was then extended to pyridine, a molecule with weak transition dipoles and some modes which spectrally interfere. The associated challenges in the experiment and data analysis are described. Finally, studies were performed to analyze the feasibility of using a heterodyne detection method to amplify weak TRIVE signals. While amplification of the signal, as well as some phase discrimination, was achieved, the studies highlighted the need for a more robust experimental implementation of the local oscillator in future experiments.