Ab-initio wave-length dependent Raman spectra: Placzek approximation and beyond

Abstract

We analyze how to obtain non-resonant and resonant Raman spectra within the Placzek as well as the Albrecht approximation. Both approximations are derived from the matrix element for light scattering by application of the Kramers, Heisenberg and Dirac formula. It is shown that the Placzek expression results from a semi-classical approximation of the combined electronic and vibrational transition energies. Molecular hydrogen, water and butadiene are studied as test cases. It turns out that the Placzek approximation agrees qualitatively with the more accurate Albrecht formulation even in the resonant regime for the excitations of single vibrational quanta. However, multiple vibrational excitations are absent in Placzek, but can be of similar intensities as single excitations under resonance conditions. The Albrecht approximation takes multiple vibrational excitations into account and the resulting simulated spectra exhibit good agreement with experimental Raman spectra in the resonance region as well.

resubmission

References in corpus (4)

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• Strong exciton regulation of Raman scattering in monolayer dichalcogenides
• Significant contributions of Albrecht's $A$ term to non-resonant Raman scattering processes
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Cited by in corpus (4)

• GPAW: An open Python package for electronic-structure calculations
• Explicit core-hole single-particle methods for L- and M- edge X-ray absorption and electron energy-loss spectra
• Nonequilibrium DMFT approach to time-resolved Raman spectroscopy
• Quasi-classical simulations of resonance Raman spectra based on path integral linearization