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5491256 
Journal Article 
The methylene chloride radical cation and its distonic isomers in the gas phase11Dedicated to professor Nico M. M. Nibbering, a leading figure in European mass spectrometry for more than 30 years 
Petersen, AC; Hammerum, S 
2001 
Yes 
International Journal of Mass Spectrometry
ISSN: 1387-3806 
210-211 
403-415 
Metastable methylene chloride radical cations react spontaneously by loss of a chlorine atom with an apparent kinetic isotope effect of 9 ± 1 and a kinetic energy release of <1 meV. It is difficult to account for an isotope effect of this magnitude, inasmuch as the zero-point vibrational energy differences are very small; the decay of an electronically excited state to the ground state may be involved. The stable molecular ions are very reactive toward collision induced dissociation, and the predominant reactions are collision induced even at very high vacuum. Similar behavior is observed for 1,1-dibromoethane radical cations, whose spontaneous reactions almost exclusively result in loss of 79Br·. The H–Cl–CHCl·+ distonic isomer of the methylene chloride radical cation reacts exclusively by loss of a chlorine atom, presumably after rearrangement to the methylene chloride radical cation. The 35Cl/37Cl ratio observed is 1.27 ± 0.01. The kinetic energy release associated with this reaction is moderate. It did not prove possible to prepare the CH2–Cl–Cl·+ distonic isomer of the methylene chloride radical cation. 
Heavy atom isotope effects; isomerization; ab initio calculations