Hyper Raman spectra calculated in a time-dependent Hartree–Fock method

Abstract

Hyper Raman scattering (HRS) of the benzonitrile (BN) and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) molecules is studied by means of ab initio calculations. The computational procedure employs a recently developed methodology for the analytic calculations of frequency-dependent polarizability gradients of arbitrary order, including perturbation dependent basis sets. The result are compared to normal Raman scattering (NRS) and coherent anti-Stokes Raman scattering (CARS) that previously have been studied using the same technology. It is found that some suppressed or silent modes in CARS and NRS spectra are clearly seen in HRS, and that although under general excitation conditions the HRS intensities are much lower than for CARS and NRS, HRS provides complementary information useful for target identification.

Keywords:

• hyper Raman scattering
• Hartree–Fock

Acknowledgements

This work was supported by a grant from the Swedish Infrastructure Committee (SNIC) for the project ‘Multiphysics Modeling of Molecular Materials’, SNIC 023/07-18. This work has also received support from the Norwegian Research Council through a Centre of Excellence Grant (Grant No. 179568/V30) and a VIBRON Grant (Grant No. 177558/V30), as well as through a grant of computer time from the Norwegian Supercomputing Program.