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Author(s):Coudert, L. H.
Contributor(s):Kwabia Tchana, F. ; Motiyenko, R. A.; Margulès, L.
Subject(s):Mini-symposium: Large Amplitude Motions
Abstract:Doubly deuterated methanol CD$_2$HOH is a non-rigid molecule displaying internal rotation of its asymmetrical CD$_2$H methyl group. Like the isotopic species of methanol with a symmetrical CH$_3$ or CD$_3$ group, it displays a strong rotation-torsion Coriolis coupling. Unlike these species, it also displays a dependence of its generalized inertia tensor on the angle of internal rotation. Its complicated rotation-torsion spectrum was investigated in the microwave,\footnote{Liu \& Quade, {\em J.\ Mol.\ Spectrosc.}~{\bf 146} (1991) 252; Su, Liu, \& Quade, {\em J.\ Mol.\ Spectrosc.}~{\bf 149} (1991) 557; Quade, Liu, Mukhopadhyay, \& Su, {\em J.\ Mol.\ Spectrosc.}~{\bf 192} (1998) 378; Su \& Quade, {\em J.\ Chem.\ Phys.}~{\bf 90} (1989) 1396} submillimeter-wave,\footnotetext[2]{Ndao, Tchana, Coudert, Motiyenko, Margul\`es, Barros, Manceron, \& Roy, {\em J.\ Mol.\ Spectrosc.}~{\bf 326} (2015) 136}\footnotetext[3]{Mukhopadhyay, {\em Inf.\ Phys.\ Tech.}~{\bf 75} (2016) 139; {\em ibid.}~{\bf 76} (2016) 116}$^{b,c}$ terahertz,$^b$ and FIR$^{b,c}$ domains. Although more than 3000 transitions have been assigned so far, no global analysis, like the one performed for the similar species CH$_2$DOH,\footnotetext[4]{Coudert, Zemouli, Motiyenko, Margul\`es, \& Klee, {\em J.\ Chem.\ Phys.}~{\bf 140} (2014) 064307}$^d$ has been carried out. In this talk, new assignments in the terahertz and FIR spectra of CD$_2$HOH will be reported. Parallel and perpendicular transitions, characterized by a higher $K$-value than in our previous investigation,$^b$ could be identified up to $J=35$ for the three lowest lying torsional states. Using the theoretical approach developed for CH$_2$DOH,$^d$ a global analysis of the available high-resolution data has been attempted in order to check the new assignments and to retrieve spectroscopic parameters such as those describing the hindering potential and the generalized inertia tensor.\footnotetext[5]{Liu \& Quade, {\em J.\ Mol.\ Spectrosc.}~{\bf 146} (1991) 238; El Hilali, Coudert, Konov, \& Klee, {\em J.\ Chem.\ Phys.}~{\bf 135} (2011) 194309}$^e$ So far, this global analysis has been restricted to transitions with $K\geq4$ as rotation-torsion levels with $K<4$ are affected by strong rotation-torsion couplings and cannot be properly modeled. Hopefully this issue will be dealt with by the time of the Symposium.
Issue Date:22-Jun-20
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Date Available in IDEALS:2020-06-26

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