Global Fit of Rotational Transitions in the Ground Torsional State of Methanol

✍ Scribed by L.H. Xu; J.T. Hougen

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 735 KB
• Volume: 169
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1995.1032

✦ Synopsis

We have carried out a global fit of a (v_{\mathrm{t}}=0) and (J \leqslant 20) methanol data set containing some 730 microwave lines ((K \leqslant 12)) and 1320 Fourier-transform far-infrared transitions ((K \leqslant 14)), using a theoretical model and computer program successfully applied previously to acetaldehyde torsionrotation levels below the barrier. Microwave lines were assigned a measurement uncertainty of either (4 \mathrm{kHz}) (supersonic jet Fourier-transform measurements) or (50 \mathrm{kHz}). Far-infrared lines were assigned a measurement uncertainty of (0.0002 \mathrm{~cm}^{-1}). A very satisfactory fit was obtained with 43 adjusted and 3 fixed parameters, yielding an overall weighted standard deviation of 1.04. (It must be noted, however, that microwave measurements with (K \geqslant 13) had to be excluded from the fit.) We conclude that the existing model is capable of fitting (v_{1}=0) methanol rotational transitions to experimental accuracy, provided that (K) values are restricted as stated above. We believe that interactions of high- (K v_{1}=0) levels with low- (K v_{t}=1) levels, leading to level shifts on the order of a few MHz, is the cause of our high- (K) fitting difficulties. (c) 1995 Academic Press. Inc.