Time- and frequency-resolved coherent two-dimensional IR spectroscopy: Its complementary relationship with the coherent two-dimensional Raman scattering spectroscopy

A theoretical description of the coherent two-dimensional IR spectroscopy is presented. Two consecutive IR pulses can be used to create two consecutive vibrational coherence states. The third off-resonant optical pulse is used to probe the two-dimensional transient grating thus created and then the scattered field is measured. The corresponding nonlinear response functions are obtained in the analytic forms by assuming that the vibrational modes are weakly anharmonic Brownian oscillators. Since one can experimentally control the two delay times as well as the two IR field frequencies, it is possible to extract vital information on the vibrational relaxation in time domain as well as the intra- and intermolecular vibrational mode couplings in frequency domain. Numerical calculations are carried out to clarify the quantitative features of the coherent 2D IR spectroscopic phenomenon. (C) 1998 American Institute of Physics. [S0021-9606(98)03048-7].