A time averaged semiclassical approach to IR spectroscopy

We propose a new semiclassical approach to the calculation of molecular IR spectra. The method employs the time averaging technique of Kaledin and Miller upon symmetrization of the quantum dipole–dipole autocorrelation function. Spectra at high and low temperatures are investigated. In the first cas...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of chemical physics 2024-06, Vol.160 (21)
Main Authors: Lanzi, Cecilia, Aieta, Chiara, Ceotto, Michele, Conte, Riccardo
Format: Article
Language:English
Subjects:
Autocorrelation functions
Dipoles
Infrared spectroscopy
Line shape
Low temperature
Molecular absorption
Power spectra
Spectrum analysis
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We propose a new semiclassical approach to the calculation of molecular IR spectra. The method employs the time averaging technique of Kaledin and Miller upon symmetrization of the quantum dipole–dipole autocorrelation function. Spectra at high and low temperatures are investigated. In the first case, we are able to point out the possible presence of hot bands in the molecular absorption line shape. In the second case, we are able to reproduce accurate IR spectra as demonstrated by a calculation of the IR spectrum of the water molecule, which is within 4% of the exact intensity. Our time averaged IR spectra can be directly compared to time averaged semiclassical power spectra as shown in an application to the CO2 molecule, which points out the differences between IR and power spectra and demonstrates that our new approach can identify active IR transitions correctly. Overall, the method features excellent accuracy in calculating absorption intensities and provides estimates for the frequencies of vibrations in agreement with the corresponding power spectra. In perspective, this work opens up the possibility to interface the new method with the semiclassical techniques developed for power spectra, such as the divide-and-conquer one, to get accurate IR spectra of complex and high-dimensional molecular systems.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0214037