Peak shapes in femtosecond 2D correlation spectroscopy Original Research Article

The two-dimensional (2D) peak shape correlates the electronic frequencies of individual molecules during initial absorption and subsequent radiation. Because the two spectra from each molecule are correlated before addition to produce a macroscopic signal, the 2D peak shape contains new microscopic information about the dynamics of individual molecular environments. Peak shapes in 2D femtosecond spectroscopy are investigated computationally with the Brownian oscillator model of Yan and Mukamel, which incorporates time-resolved spontaneous solvent fluctuations and forced solvent reorganization after excitation. These computations reveal the origin of the off-diagonal displacement of the diagonal 2D peaks, the negative region above the diagonal, and the peak shape distortions produced by manipulation of the phase-matched response with noncollinear pulses.