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 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. Subject(s): Large amplitude motions, internal rotation Abstract: Hyperfine splittings in the ground state of CH$_{3}$OH have recently been studied by several groups [JCP(2015)143$\textunderscore$044304, (2016)145$\textunderscore$024307, (2016)145$\textunderscore$244301]. In our work [JCP(2016)145$\textunderscore$024307], we treated splittings in the Lamb-dip sub-mm-wave transitions between some torsion-rotation states of $\it{E}$ symmetry. These doublets increase nearly linearly with $\it{J}$, 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 $\it{E}$ torsional state of CH$_{3}$OH from three laboratories. Four series of lines dominate the available data. Measurements are: (i) from Kharkov/Lille, K = 6 $\leftarrow$ 7, $\it{Q}$ branch, quartets, with 7 $\leq$ $\it{J}$ $\leq$ 15; (ii) from NNOV, $\it{K}$ = 3 $\leftarrow$ 2, $\it{Q}$ branch, with 3 $\leq$ $\it{J}$ $\leq$ 18, where the series starts as quartets, changes to doublets at $\it{J}$ = 7, and then finally to singlets at $\it{J}$ = 17; (iii) from NNOV, $\it{K}$ = -2 $\leftarrow$ -3, $\it{P}$ branch, doublets, with 8 $\leq$ $\it{J}$ $\leq$ 12; (iv) from Kharkov/Lille, $\it{K}$ = 8 $\leftarrow$ 7, $\it{Q}$ branch, with 8 $\leq$ $\it{J}$ $\leq$ 24, where the series starts as triplets and becomes doublets at $\it{J}$ = 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 $\it{I}$ = $\frac{1}{2}$ spin systems arising from the OH and CH$_{3}$ protons, respectively. Work is in progress to understand the deeper physical meaning of these fitting parameters and compare them with ab initio calculations. Issue Date: 06/19/18 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/100552 DOI: 10.15278/isms.2018.TK06 Other Identifier(s): TK06 Date Available in IDEALS: 2018-08-172018-12-12
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