2D THz-THz-Raman Photon-Echo Spectroscopy of Molecular Vibrations in Liquid Bromoform
Fundamental properties of molecular liquids are governed by long-range interactions that most prominently manifest at terahertz (THz) frequencies. Here we report the detection of nonlinear THz photon-echo (rephasing) signals in liquid bromoform using THz-THz-Raman spectroscopy. Together, the many observed signatures span frequencies from 0.5 to 8.5 THz and result from couplings between thermally populated ladders of vibrational states. The strongest peaks in the spectrum are found to be multiquantum dipole and 1-quantum polarizability transitions and may arise from nonlinearities in the intramolecular dipole moment surface driven by intermolecular interactions.
© 2017 American Chemical Society. Received: August 10, 2017; Accepted: September 6, 2017; Published: September 6, 2017. We acknowledge Dr. Mostafa Shalaby (Paul Scherrer Institut, Switzerland) for suggesting the use of a diamond window and polarizer beam combiner and the National Science Foundation (Grants CHE-1214123 and CHE-1057112) for financial support. We also thank Matt Welborn, Ioan Magdau, Brett Savoie, and Feizhi Ding for helpful discussions. R.W. acknowledges financial support from the Deutsche Forschungsgemeinschaft under grant number WE 5762/1-1. M.A.A. acknowledges current support from a Yen Postdoctoral Fellowship from the Institute for Biophysical Dynamics at the University of Chicago. The authors declare no competing financial interest.
Supplemental Material - jz7b02106_si_001.pdf