Abstract-Nonlinear terahertz coherent excitation of vibrational modes of liquids

                                     

Marco A. Allodi^1,a), Ian A. Finneran¹ and Geoffrey A. Blake^1,2,b)
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a) mallodi@uchicago.edu; Current address: Department of Chemistry, The Institute for 
b) gab@gps.caltech.edu
Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
J. Chem. Phys. 143, 234204 (2015); http://dx.doi.org/10.1063/1.4938165

http://scitation.aip.org/content/aip/journal/jcp/143/23/10.1063/1.4938165

We report the first coherent excitation of intramolecular vibrational modes via the nonlinear interaction of a TeraHertz (THz) light field with molecular liquids. A terahertz-terahertz-Raman pulse sequence prepares the coherences with a broadband, high-energy, (sub)picosecond terahertz pulse, that are then measured in a terahertz Kerr effect spectrometer via phase-sensitive, heterodyne detection with an optical pulse. The spectrometer reported here has broader terahertz frequency coverage, and an increased sensitivity relative to previously reported terahertz Kerr effect experiments. Vibrational coherences are observed in liquid diiodomethane at 3.66 THz (122 cm⁻¹), and in carbon tetrachloride at 6.50 THz (217 cm⁻¹), in exact agreement with literature values of those intramolecular modes. This work opens the door to 2D spectroscopies, nonlinear in terahertz field, that can study the dynamics of condensed-phase molecular systems, as well as coherent control at terahertz frequencies.