Raman excitation profiles with self-consistent excited-state displacements

Raman excitation profiles (REPs) are computed in the time domain for harmonic modes with excited-state displacement g and measured at multiple excitation frequencies omega (L) in a bimetallic complex with a metal-to-metal charge-transfer band and 10 coupled modes. Self-consistency is required because the time evolution depends on all displaced modes rather than the individual intensities used in the short-time approximation for g((0)),. Self-consistency ensures that g is independent of wt for a single resonance. Exact REPs for displaced oscillators show the importance of vibronic lifetimes and marked deviations from the short-time approximation ac. molecular frequencies. Spectra at multiple wt indicate scattering from another electronic excitation with displacement h that is also found self-consistently. Mode-specific Raman data at multiple wt require additional parameters to yield reliable structural information. Harmonic oscillators with self-consistent displacements are a first approximation to systems with many coupled modes.