Collision-induced rototranslational absorption in compressed methane gas

Journal Article · Sat Oct 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.042715· OSTI ID:20718751

Buser, Michael; Frommhold, Lothar ^[1]

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1. Physics Department, University of Texas, Austin, Texas 78712 (United States)

The collision-induced, rototranslational absorption spectrum of compressed methane gas is computed, based purely on the reliably known, leading multipole-induced dipole components of CH{sub 4} molecular pairs. In contrast to previous work of the kind no ad hoc empirical corrections of unknown exchange force-induced dipole components are attempted. Not surprisingly, the calculated spectra show a sizeable absorption defect at virtually all frequencies, when compared to existing laboratory measurements. The defect suggests the presence of dipole-induction mechanisms in addition to those due to the leading multipole-induced dipole terms. The excess absorption, the differences between measured and calculated spectra, resembles in certain ways the excess absorption spectra seen at the same frequencies in methane-X gas mixtures, where X stands for helium, hydrogen, or nitrogen, respectively [Buser and Frommhold, J. Chem. Phys. 122, 024301 (2005)]. To a large extent, the excess absorption seems to be related to collisional distortions of the tetrahedral frame of the unperturbed CH{sub 4} molecule.

• OSTI ID: 20718751
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 4 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ABSORPTION SPECTRA
CORRECTIONS
DIPOLES
HELIUM
HYDROGEN
INFRARED SPECTRA
METHANE
MIXTURES
MOLECULE-MOLECULE COLLISIONS
MOLECULES
NITROGEN
ROTATIONAL STATES