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Updated: Jun 24, 2026

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies
Published on: December 18, 2015
Mechanisms for the far-infrared absorption in liquid methane
1Grupo de Química Teórica, Instituto de Química, UFRGS, Porto Alegre, RS-91540-000, Brazil.
Abstract:
The time correlation function for the induced dipole moment in liquid methane was computed from molecular dynamics computer simulations for a thermodynamic state at a temperature of 122.2 K and density of 25.34 mol/l. We included first-order induction mechanisms from the electric fields emanated by octupole and hexadecapole moments, their field gradients, as well as electronic superposition. The octupole-induced dipole represents the most important contribution to the far-infrared absorption spectrum. However, additional mechanisms are important for absorption in liquid methane. By comparing the computed absorption line shape with the experimental spectrum, we found a very satisfactory agreement between the two if we account for detailed balancing.
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