Low-frequency anharmonic couplings in crystalline bromoform: Theory

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Anharmonic couplings are crucial for understanding molecular dynamics and vibrational spectroscopy.
• The 2D Raman-THz response provides insights into coupled intra- and intermolecular vibrational modes.

Purpose of the Study:

• To theoretically investigate low-frequency anharmonic couplings in crystalline bromoform.
• To elucidate the contributions of electrical and mechanical anharmonicities to the 2D Raman-THz response.

Main Methods:

• Density functional theory (DFT) quantum chemistry calculations.
• Calculation of electrical and mechanical anharmonicities for intra- and intermolecular modes.

Main Results:

• Electrical anharmonicity was found to dominate cross-peak intensities in the 2D Raman-THz spectra of bromoform.
• The C3v symmetry and orientational averaging explain observed differences in peak intensities.

Conclusions:

• The theoretical model accurately reproduces experimental 2D Raman-THz response data for bromoform.
• Anharmonic coupling between intra- and intermolecular modes is confirmed as the origin of the observed spectral features.