Systematic investigation of coupling between symmetric and antisymmetric stretches of D2O in CHCl3 by 2D IR.

The coupling between the symmetric (νs) and antisymmetric (νa) OD stretch modes of monomeric D2O in CHCl3 is investigated using polarization-dependent two-dimensional infrared (2D IR) spectroscopy supported by numerical 2D IR simulations based on the exciton-band theory. The relationship between the local modes' and the exciton states' parameters is systematically studied, including center frequencies, diagonal anharmonicities, coupling, and off-diagonal anharmonicity. The mean coupling between νs and νa is accurately evaluated to be -49.96 ± 0.14 cm-1. The degree of relaxation in the harmonic approximation is quantified, and the angle between the exciton-state dipoles is accurately evaluated to be 101.4° ± 3.6°. In addition, the effect of the local-mode frequency correlation on the resulting exciton-state frequency correlation and the spectral shape of the linear and 2D IR spectra are also investigated.