ORBi: Remacle Françoise - AN ABINITIO STUDY OF THE ISOMERIZATION AND FRAGMENTATION OF CHO2+ IONS

Reference : AN ABINITIO STUDY OF THE ISOMERIZATION AND FRAGMENTATION OF CHO2+ IONS - AN EXAMPLE OF S...


	Document type :	Scientific journals : Article
	Discipline(s) :	Physical, chemical, mathematical & earth Sciences : Physics
	To cite this reference:	http://hdl.handle.net/2268/3544

Title :	AN ABINITIO STUDY OF THE ISOMERIZATION AND FRAGMENTATION OF CHO2+ IONS - AN EXAMPLE OF SPIN-CONTROLLED REACTIONS
Language :	English
Author, co-author :	Remacle, Françoise [Université de Liège - ULg > Département de chimie (sciences) > Laboratoire de chimie physique théorique >]
	Petitjean, Serge [ > > ]
	Dehareng, Dominique [Université de Liège - ULg > > Centre d'ingénierie des protéines >]
	Lorquet, Jean-Claude [Université de Liège - ULg > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences) >]
Publication date :	1987
Journal title :	International Journal of Mass Spectrometry and Ion Processes
Publisher :	Elsevier
Volume :	77
Issue/season :	2-3
Pages :	187-201
Audience :	International
ISSN :	0168-1176
City :	Amsterdam
Country :	The Netherlands
Keywords :	[en] isomers of CHO2+ ; fragmentation of CHO2+
Abstract :	[en] [CHO2+] ions exist in two isomeric forms, a quasi-linear carboxylic structure, OCOH+ (I), and a formate structure, O(CH)O+ (II). The latter is known to isomerise into the former with a low rate constant (about 105 s−1). Configuration interaction ab initio calculations reveal that the ion can exist in three low-lying electronic states of different multiplicity and symmetry species, a singlet (Image 1A′) and two triplets (ã3A′ and Image 3A′'). The potential energy surfaces cross so that the nature of the lowest state varies as a function of the nuclear geometry. The singlet surface (Image 1A′) has its deepest minimum for structure I and a subsidiary minimum for structure II. The situation is reversed for the ã3A′ state which has its deepest minimum for structure II and which exhibits a shallow minimum for structure I. Thus, at low energies, the carboxylic and formate ions are respectively in a singlet and in a triplet state. These ions lose an oxygen atom on a microsecond time scale by a composite mechanism which is subject to a large isotope effect. One of the components of the metastable peak corresponds to reaction OCOH+(1A') -> O(CH)O+ (3A') -> HCO+ + O giving rise to a small kinetic energy release. The second component is due to a spin-orbit controlled direct predissociation process, viz. OCOH+ (1A') -> OCOH+ (3A') -> HOC+ + O. The probability of surface hopping varies as a function of the internal energy between 0 and a maximum value of ca. 0.008. The corresponding kinetic energy release is expected to be larger for the deuterated than for the hydrogenated compound. Thus, the two components are resolved in the deuterated compound, but hardly distinguishable in the hydrogenated species.
Funders :	Politique Scientifique Fédérale (Belgique) = Belgian Federal Science Policy ; Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS
Target :	Researchers ; Professionals ; Students
Permalink :	http://hdl.handle.net/2268/3544

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