Group-Theoretical Treatment of Tunneling Splittings in the Methanol Dimer

✍ Scribed by N. Ohashi; J.T. Hougen

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 862 KB
• Volume: 163
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1994.1010

✦ Synopsis

Tunneling splitting patterns, selection rules, and effective (B) values for (K=0) rotational levels of the hydrogen-bonded methanol dimer are predicted from group-theoretical considerations, a modified internal axis method, approximate descriptions of possible tunneling paths, and the assumption that (K=0) levels can be treated by themselves. It is shown that 25 different tunneling motions are possible when the two methanol monomers are identical, giving rise to 16 tunnelingrotational levels for (K=0) : four nondegenerate (A) levels, eight doubly degenerate (E) levels, and four fourfold degenerate (G) levels. The gross features of a recently observed methanol dimer (K=) (0 a)-type microwave spectrum can be explained using only two of these tunneling motions, namely the internal rotation of each of the two inequivalent methyl groups in the dimer. Finer details of the observed splittings presumably arise from some of the remaining 23 tunneling motions. Tunneling splitting patterns are also predicted for cases in which the two methanols in the dimer are isotopically different, but the (C_{3 k}) symmetry of both methyl tops is preserved. & 1994 Academic Press. Inc.