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The Relaxation Matrix for Symmetric Tops with Inversion Symmetry. I. Effects of Line Coupling on Self-Broadened v (sub 1) and Pure Rotational Bands of NH3The Robert-Bonamy formalism has been commonly used to calculate half-widths and shifts of spectral lines for decades. This formalism is based on several approximations. Among them, two have not been fully addressed: the isolated line approximation and the neglect of coupling between the translational and internal motions. Recently, we have shown that the isolated line approximation is not necessary in developing semi-classical line shape theories. Based on this progress, we have been able to develop a new formalism that enables not only to reduce uncertainties on calculated half-widths and shifts, but also to model line mixing effects on spectra starting from the knowledge of the intermolecular potential. In our previous studies, the new formalism had been applied to linear and asymmetric-top molecules. In the present study, the method has been extended to symmetric-top molecules with inversion symmetry. As expected, the inversion splitting induces a complete failure of the isolated line approximation. We have calculated the complex relaxation matrices of selfbroadened NH3. The half-widths and shifts in the ν1 and the pure rotational bands are reported in the present paper. When compared with measurements, the calculated half-widths match the experimental data very well, since the inapplicable isolated line approximation has been removed. With respect to the shifts, only qualitative results are obtained and discussed. Calculated off-diagonal elements of the relaxation matrix and a comparison with the observed line mixing effects are reported in the companion paper (Paper II).
Document ID
20160007918
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ma, Q. (Columbia Univ. New York, NY, United States)
Boulet, C. (Centre National de la Recherche Scientifique Orsay, France)
Date Acquired
June 27, 2016
Publication Date
June 9, 2016
Publication Information
Publication: Journal of Chemical Physics
Volume: 144
Issue: 22
Subject Category
Atomic and Molecular Physics
Report/Patent Number
GSFC-E-DAA-TN33255
Funding Number(s)
CONTRACT_GRANT: DOE DEAC02-05CH11231
CONTRACT_GRANT: NSF 1501297
CONTRACT_GRANT: NNX14AB99A
Distribution Limits
Public
Copyright
Other
Keywords
Trajectory models
Angular momentum
Electric dipole moments
Fourier transforms
Eigenvalues