REINVESTIGATION OF THE GROUND AND FIRST TORSIONAL STATES OF METHYLFORMATE
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Date
2007
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Publisher
Ohio State University
Abstract
We have reinvestigated the laboratory spectrum for the methylformate molecule involving both the ground and first torsional states. We have fitted within almost experimental accuracy a data set for HCOOCH$_3$ consisting of 3496 v$_t$=0 and 774 v$_t$=1 microwave lines, using the so-called "rho axis method" (RAM) and a model extended to include perturbation terms through eight order. The previously published v$_t$=0 and v$_t$=1 microwave lines covering J values up to 43 in the ground and up to 18 in the first excited states have been extended by new measurements from Lille with maximum values of J = 62. The final fit requires only 49 parameters to achieve a weigthed standard deviation for the whole fit of 1.43 for a total of 4270 lines. This result represents an improvement over the previous fit which achieved a standard deviation of 1.96 for 3862 lines using 69 parameters. A calculation of the linestrengths of torsion-rotation transition up to J=60 needed for the astronomical survey is also presented.
Description
Author Institution: Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universitad de Huelva, 21071 Huelva, Spain; Laboratoire de Physique des Lasers, Atomes et Molecules, CNRS et Universite de Lille I, F-59655, Villeneuve d'Ascq Cedex, France; Laboratoire Interuniversitaire des Systemes Atmospheriques, CNRS et Universites Paris 7 et Paris 12, 61 av. General de Gaulle, 94010, Creteil, France