Hyperfine splittings of methanol in the first excited torsional state

Xu, Li-Hong

Permalink

https://hdl.handle.net/2142/100552 Copy

Description

Title

Hyperfine splittings of methanol in the first excited torsional state

Author(s)

Xu, Li-Hong

Contributor(s)

• Bailleux, Stephane
• Motiyenko, R. A.
• Margulès, L.
• Krapivin, Igor
• Alekseev, E. A.
• Lapinov, Alexander
• Belov, Sergey
• Golubiatnikov, G. Yu
• Hougen, Jon T.

Issue Date

2018-06-19

Keyword(s)

Large amplitude motions, internal rotation

Abstract

Hyperfine splittings in the ground state of CH3OH have recently been studied by several groups [JCP(2015)143 044304, (2016)145 024307, (2016)145 244301]. In our work [JCP(2016)145 024307], we treated splittings in the Lamb-dip sub-mm-wave transitions between some torsion-rotation states of E symmetry. These doublets increase nearly linearly with J , and we attributed them to the effect of torsionally mediated spin-rotation interaction of the methyl protons. Hyperfine doublets of this type have so far been observed only in methanol. The focus of this talk is on hyperfine doublet, ”triplet” and quartet splittings observed in the first excited E torsional state of CH3OH from three laboratories. Four series of lines dominate the available data. Measurements are: (i) from Kharkov/Lille, K = 6 ← 7, Q branch, quartets, with 7 ≤ J ≤ 15; (ii) from NNOV, K = 3 ← 2, Q branch, with 3 ≤ J ≤ 18, where the series starts as quartets, changes to doublets at J = 7, and then finally to singlets at J = 17; (iii) from NNOV, K = -2 ← -3, P branch, doublets, with 8 ≤ J ≤ 12; (iv) from Kharkov/Lille, K = 8 ← 7, Q branch, with 8 ≤ J ≤ 24, where the series starts as triplets and becomes doublets at J = 15. We have ignored the central features of the triplets, since we believe they might be due to unusual double-N crossover resonances; and (v) a few measurements that don’t form branches. We have empirically modeled these hyperfine splittings with spin-torsion, spin-rotational and spin-spin terms for the two I = 1 2 spin systems arising from the OH and CH3 protons, respectively. Work is in progress to understand the deeper physical meaning of these fitting parameters and compare them with ab initio calculations.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100552

DOI

10.15278/isms.2018.TK06

Copyright and License Information

Copyright 2018 Li-Hong Xu

Owning Collections