Interference, dephasing, and vibrational coupling effects between coherence pathways in doubly vibrationally enhanced nonlinear spectroscopies

Doubly vibrationally enhanced (DOVE) four-wave mixing is capable of producing coherent two-dimensional (2D) vibrational spectra with cross-peaks that reflect intramolecular and intermolecular mode coupling. These methods are based on double vibrational coherences that are analogous to the double spin coherences in 2D nuclear magnetic resonance methods. In particular, there are two pathways for DOVE infrared spectroscopy that interfere to change the line shapes of doubly resonant cross-peaks. The interference depends on the relative dephasing rates of the coherences involved in the different pathways. We derive relationships between the dephasing rates of the different coherences in DOVE pathways and show how these relationships affect the line shapes of DOVE resonances. Comparisons are made with experimental 2D DOVE spectra. (C) 2001 Elsevier Science B.V. All rights reserved.