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Title:EXPERIMENTAL AND COMPUTATIONAL INVESTIGATIONS OF THE THRESHOLD PHOTOELECTRON SPECTRUM OF THE HCCN RADICAL
Author(s):Coudert, L. H.
Contributor(s):Loison, J.-C.; Küger, J.; Garcia, Gustavo A.; Falvo, Cyril; Gans, B.
Subject(s):Comparing theory and experiment
Abstract:The \ce{HCCN} radical, already detected in the interstellar_x000d_ medium, is also important for nitrile chemistry in Titan's_x000d_ atmosphere.\footnote{Gu\'elin and Cernicharo, {\em A\&A}~{\bf_x000d_ 244} (1991) L21; Loison {\em et al.,} {\em Icarus}~{\bf 247} (2015)_x000d_ 218} Quite recently the photoionization spectrum of the radical_x000d_ has been recorded\footnote{\label{spectrum}Garcia, Kr\"uger,_x000d_ Gans, Falvo, Coudert, and Loison, {\em J.\ Chem.\ Phys.}~(2017)_x000d_ submitted} using mass selected threshold photoelectron (TPE)_x000d_ spectroscopy and this provided us with the first spectroscopic_x000d_ information about the \ce{HCCN+} cation. Modeling such a_x000d_ spectrum requires accounting for the non-rigidity of \ce{HCCN}_x000d_ and for the Renner-Teller effect in \ce{HCCN+}._x000d_ _x000d_ In its $^3A''$ electronic ground state, HCCN is_x000d_ a non-rigid molecule as the potential_x000d_ for the $\angle{\ce{HCC}}$ bending angle is very_x000d_ shallow.\footnote{Koput, {\em J.\ Phys.\ Chem.\ A}~{\bf 106}_x000d_ (2002) 6183} Vibronic couplings with the same_x000d_ bending angle leads, in the $^2\Pi$ electronic ground state of_x000d_ \ce{HCCN+}, to a strong Renner-Teller effect giving rise to a_x000d_ bent $^2A'$ and a quasi-linear $^2A''$ state.\footnote{Zhao,_x000d_ Zhang, and Sun, {\em J.\ Phys.\ Chem.\ A}~{\bf 112} (2008)_x000d_ 12125}_x000d_ _x000d_ In this paper the photoionization spectrum of the HCCN radical_x000d_ is simulated. The model developped treats the $\angle{\ce{HCC}}$ bending_x000d_ angle as a large amplitude coordinate in both the radical_x000d_ and the cation and accounts for the overall rotation and_x000d_ the Renner-Teller couplings. Gaussian quadrature are used_x000d_ to calculate matrix elements of the three potential energy_x000d_ functions retrieved through {\em ab initio} calculations_x000d_ and rovibrational operators going to infinity for the linear_x000d_ configuration are treated rigorously._x000d_ _x000d_ The HCCN TPE spectrum is computed with the above model_x000d_ calculating all rotational components and choosing the_x000d_ appropriate lineshape. This synthetic spectrum will be_x000d_ shown in the paper and compared with the experimental_x000d_ one.$^b$
Issue Date:6/19/2017
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:CONFERENCE PAPER/PRESENTATION
Type:Text
Language:English
URI:http://hdl.handle.net/2142/96831
DOI:10.15278/isms.2017.MI01
Date Available in IDEALS:2017-07-27


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