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 ωL 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 ωL for a single resonance. Exact REPs for displaced oscillators show the importance of vibronic lifetimes and marked deviations from the short-time approximation at molecular frequencies. Spectra at multiple ωL indicate scattering from another electronic excitation with displacement h that is also found self-consistently. Mode-specific Raman data at multiple ωL require additional parameters to yield reliable structural information. Harmonic oscillators with self-consistent displacements are a first approximation to systems with many coupled modes.