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Author(s):Coudert, L. H.
Contributor(s):Pirali, Olivier; Martin-Drumel, Marie-Aline
Subject(s):Large amplitude motions, internal rotation
Abstract:The ce{NH2} radical spectrum, first observed by Herzberg and_x000d_ Ramsay,footnote{Herzberg and Ramsay, {em J. Chem._x000d_ Phys.}~{bf 20} (1952) 347} is dominated by a strong_x000d_ Renner-Teller effectfootnote{Dressler and Ramsay, {em Phil._x000d_ Trans. R. Soc. A}~{bf 25} (1959) 553} giving rise to two_x000d_ electronic states: the bent $X, ^{2!}B_1$ ground state and_x000d_ the quasi-linear $A, ^{2!}A_1$ excited state. The ce{NH2}_x000d_ radical has been the subject of numerous high-resolution_x000d_ investigations and its electronic and ro-vibrational_x000d_ transitionsfootnote{label{data}Hadj Bachir, Huet,_x000d_ Destombes, and Vervloet, {em J. Molec. Spectrosc.}~{bf_x000d_ 193} (1999) 326; McKellar, Vervloet, Burkholder, and Howard,_x000d_ {em J. Molec. Spectrosc.}~{bf 142} (1990) 319; Morino_x000d_ and Kawaguchi, {em J. Molec. Spectrosc.}~{bf 182} (1997)_x000d_ 428} have been measured. Using synchrotron radiation, new_x000d_ rotational transitions have been recently recorded and a_x000d_ value of the rotational quantum number $N$ as large as 26_x000d_ could be reached.footnote{label{mam}Martin-Drumel, Pirali,_x000d_ and Vervloet, {em J. Phys. Chem. A}~{bf 118} (2014)_x000d_ 1331} In the $X, ^{2!}B_1$ ground state, the ce{NH2} radical_x000d_ behaves like a triatomic molecule displaying spin-rotation_x000d_ splittings. Due to the lightness of the molecule, a strong_x000d_ coupling between the overall rotation and the bending_x000d_ mode arises whose effects increase with $N$ and lead to_x000d_ the anomalous centrifugal distortion evidenced in the new_x000d_ measurements.$^d$_x000d_ _x000d_ In this talk the Bending-Rotation approachfootnote{Coudert,_x000d_ {em J. Molec. Spectrosc.}~{bf 165} (1994) 406} developed_x000d_ to account for the anomalous centrifugal distortion of the_x000d_ water molecule is modified to include spin-rotation_x000d_ coupling and applied to the fitting of high-resolution data_x000d_ pertaining to the ground electronic state of ce{NH2}._x000d_ A preliminary line position analysis of the available_x000d_ data$^{c,d}$ allowed us to account_x000d_ for 1681 transitions with a unitless standard deviation of 1.2._x000d_ New transitions could also be assigned in the spectrum recorded_x000d_ by Martin-Drumel {em et al.}$^d$_x000d_ In the talk, the results obtained with the new theoretical_x000d_ approach will be compared to those retrieved with a Watson-type_x000d_ Hamiltonian and the effects of the vibronic coupling between_x000d_ the ground $X, ^{2!}B_1$ and the excited $A, ^{2!}A_1$ electronic_x000d_ state will be discussed.
Issue Date:6/20/2017
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Date Available in IDEALS:2017-07-27

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