Surface collisions of the acetonitrile molecular ion:: evidence for isomerization of CD3CN•+ to the ketenimine cation CD2=C=ND•+

Reactions induced by the impact of acetonitrile and deuterated acetonitrile molecular ions on a hydrocarbon-covered stainless steel surface were investigated using a recently constructed tandem mass spectrometer (BESTOF). Mass spectra of product ions formed were recorded for projectile collision energies in the range of about 5-70 eV. Both, simple dissociations of the projectile ion and chemical reactions involving H-atom transfer from the surface material (followed by subsequent dissociation of the protonated projectile ion formed) were observed. In particular, formation of CD2H+ and CD3+ via dissociation of the surface-protonated deuterated acetonitrile ion CD3CNH+ and the collision energy dependence of their relative abundance indicate substantial degree of isomerization of the acetonitrile molecular radical cation CD3CN.+ to the ketenimine ion CD2=C=ND.+. The isomerization seems to take place upon electron impact ionization of the acetonitrile molecule in the ion source preceding the tandem mass spectrometer. (C) 2002 Elsevier Science B.V. All rights reserved.