Two-dimensional vibrational spectroscopy. II. Ab initio calculation of the coherent 2D infrared response function of CHCl₃ and comparison with the 2D Raman response function

The two-dimensional vibrational spectroscopy involving two infrared (IR) pulses and a single optical pulse, which was theoretically proposed recently [J. Chem. Phys. 109, 10559 (1998)], is studied by using the ab initio calculation method for CHCl₃. By obtaining the first- and second-order derivatives of the molecular dipole moment as well as the polarizability, the coherent 2D IR response function and its spectrum are calculated with an assumption that the vibrational dynamics can be described by the Brownian oscillator model. The origin of each peak in the entire coherent 2D IR spectrum is discussed in detail, and is directly compared with the coherent 2D Raman scattering spectrum of CHCl₃. This comparison demonstrates the complementary nature between the coherent 2D IR and Raman spectroscopies. A brief discussion on the coupling patterns is also presented.