A COMPREHENSIVE INTENSITY STUDY OF THE 4 TORSIONAL BAND OF ETHANE J. NOROOZ OLIAEE, N. Moazzen-Ahmadi Institute for Quantum Science and Technology Department of Physics and Astronomy, University of Calgary I. Ozier Department of Physics and Astronomy, University of British Columbia K. SUNG, T. CRAWFORD, L. R. BROWN Jet Propulsion Laboratory, California Institute of Technology E. H. WISHNOW Space Sciences Laboratory and Department of Physics, University of California, Berkeley V . M. DEVI Department of Physics, The College of William and Mary Canadian space agency
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A COMPREHENSIVE INTENSITY STUDY OF THE 4 TORSIONAL BAND OF ETHANE J. NOROOZ OLIAEE, N. Moazzen-Ahmadi Institute for Quantum Science and Technology Department.
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A COMPREHENSIVE INTENSITY STUDY OF THE 4 TORSIONAL BAND OF ETHANE
J. NOROOZ OLIAEE, N. Moazzen-Ahmadi Institute for Quantum Science and Technology
Department of Physics and Astronomy, University of Calgary
I. OzierDepartment of Physics and Astronomy, University of British Columbia
K. SUNG, T. CRAWFORD, L. R. BROWNJet Propulsion Laboratory, California Institute of Technology
E. H. WISHNOWSpace Sciences Laboratory and Department of Physics, University of
California, Berkeley
V. M. DEVIDepartment of Physics, The College of William and Mary
Canadian space agency
Ethane is used as a tracer in the atmospheres of Jovian planets to understand the methane cycle.
To provide high quality line parameters for HITRAN and GEISA databases.
To study torsion mediated vibrational interactions
(a) Torsional fundamental 4; (b) 24 4; (c) 9 fundamental ; (d) 9 +4 4 hot band;(e) 3 fundamental; (f) the forbidden 34 band, made bright by mixing with 9; and (g) the infrared-active difference band 12 9.
L. Borvayeh et al., JMS 250, 51 (2008).
4-state analysis for normal ethane
Simulation of the torsional bands
1 1
0 z
J J
J J
4 4( , ,v , )/ ( ', ,v ', )/4 4 4 4( , , v , ; ', , v ', ) ( , , v , ; ', , v ', ) E J K kT E J K kT
VTR
A J K J K S J K J K e eZ
Integrated intensity
2 2 2 22
4 4 4 4( , , v , ; ', , v ', ) g v , v ',PR
K m KS J K J K J
m
22 24 4 4 4
(2 1)( , , v , ; ', , v ', ) g v , v ', ( 1)
1Q
JS J K J K J J J K
J J
1J R branchm
J P branch
38 / 2N hc
Line strength
N. Moazzen-Ahmadi and I. Ozier, 126, 99-112 (1987).N. Moazzen-Ahmadi, A.R.W. McKellar, J.W.C. Johns, and I. Ozier, J. Chem. Phys. 97, 3981 (1992).
The model underestimates the intensity in the P-branchThe model overestimates the intensity in the R-branchA small dip in the residual near the band origin of the fundamental
Torsional spectrum of ethane were recorded at several temperatures between 293 K to 166 K, with the lower temperatures relevant to the stratosphere of Titan.
The previously reported dipole moment expression proved to be inadequate and it had to be extended to include a Herman-Wallis type factor and two higher order terms.
The intensity has been fitted to better than 1% for the lowest temperature spectra where interference from hot and difference bands is minimal.
A consistent set of dipole moments have been obtained which would allow us to provide HITRAN and GEISA accurate line parameters for the 35 micron band of ethane.
The results presented in this study will lead to an improved understanding of the methane cycle in planetary atmospheres; they will also permit other molecular features in the CIRS spectra to be identified.