Molecular Dynamics and Spectra. II. Diatomic Raman.
Abstract
This paper indicates that infrared and Raman rotational and fundamental vibrational-rotational spectra of dense systems (high pressure gases, liquids and solids) are essentially classical, in that they can be computed and understood from a basically classical mechanical viewpoint, with some caveats for features in which anharmonicity is important, such as the detailed shape of Q branches. It is demonstrated here, using the diatomic case as an example, that ordinary, i.e. nonresonant, Raman band contours can be computed from classical mechanics plus simple quantum corrections. Classical versions of molecular dynamics, linear response theory and ensemble averaging, followed by straightforward quantum corrections, are used to compute the pure rotational and fundamental vibrational-rotational Raman band contours of N2 for the gas phase and for solutions of N2 in different densities of gas phase Ar and in liquid Ar. The evolution is seen from multiple peaked line shapes characteristic of free rotation in the gas phase to single peaks characteristic of hindered rotation in the liquid phase. Comparison is made with quantum and correspondence principle classical gas phase spectral calculations and with experimental measurements for pure N2 and N2 in liquid Ar. Three advantages are pointed out for a classical approach to infrared and Raman spectra.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1981
- Accession Number
- ADA096072
Entities
People
- Kent R. Wilson
- Peter H. Berens
- Steven R. White
Organizations
- University of California, San Diego