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Torsion–rotation global analysis of the first three torsional states (νt = 0, 1, 2) and terahertz database for methanol

Xu, Li-Hong and Fisher, J. and Lees, R. M. and Shi, H. Y. and Hougen, J. T. and Pearson, J. C. and Drouin, B. J. and Blake, G. A. and Braakman, R. (2008) Torsion–rotation global analysis of the first three torsional states (νt = 0, 1, 2) and terahertz database for methanol. Journal of Molecular Spectroscopy, 251 (1-2). pp. 305-313. ISSN 0022-2852.

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Stimulated by recent THz measurements of the methanol spectrum in one of our laboratories, undertaken in support of NASA programs related to the Herschel Space Observatory (HSO) and the Atacama Large Millimeter Array (ALMA), we have carried out a global analysis of available microwave and high-resolution infrared data for the first three torsional states (νt = 0, 1, 2), and for J values up to 30. This global fit of approximately 5600 frequency measurements and 19 000 Fourier transform far infrared (FTFIR) wavenumber measurements to 119 parameters reaches the estimated experimental measurement accuracy for the FTFIR transitions, and about twice the estimated experimental measurement accuracy for the microwave, submillimeter-wave, and terahertz transitions. The present fit is essentially a continuation of our earlier work, but we have greatly expanded our previous data set and have added a large number of new torsion–rotation interaction terms to the Hamiltonian in our previously used computer program. The results, together with a number of calculated (but unmeasured) transitions, including their line strength, estimated uncertainty, and lower state energy, are made available in the supplementary material as a database formatted to be useful for astronomical searches. Some discussion of several open spectroscopic problems, e.g., (i) an improved notation for the numerous parameters in the torsion–rotation Hamiltonian, (ii) possible causes of the failure to fit frequency measurements to the estimated measurement uncertainty, and (iii) pitfalls to be avoided when intercomparing apparently identical parameters from the internal axis method and the rho axis method are also given.

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Blake, G. A.0000-0003-0787-1610
Additional Information:Copyright 2008 California Institute of Technology. Received 5 February 2008; revised 11 March 2008. Available online 30 March 2008. The authors thank Drs. I. Kleiner and M. Godefroid for making their acetaldehyde (CH3CHO) internal rotation global fitting program available for this work. L.H.X. and R.M.L. thank the Natural Sciences and Engineering Research Council of Canada for financial support of this research program. J. Fisher is grateful for NSERC-USRA (Undergraduate Summer Research Award) support. Portions of the research described in this paper were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2008 California Institute of Technology. Government sponsorship acknowledged. Supplementary data for this article are available on ScienceDirect ( and as part of the Ohio State University Molecular Spectroscopy Archives ( Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jms.2008.03.017.
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Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords:Large amplitude internal rotational motion; Microwave; Millimeter wave; Terahertz; Global modeling; Fourier transform
Issue or Number:1-2
Record Number:CaltechAUTHORS:XULjms08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11960
Deposited By: Archive Administrator
Deposited On:14 Oct 2008 04:42
Last Modified:03 Oct 2019 00:24

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