Dissociation of Cyclobutane Molecule—Ions Formed in Charge Exchange Collisions

Abstract

Mass spectra of cyclobutane resulting from charge exchange with slow positive ions have been determined. Product ion intensities were plotted as a function of the energy absorbed by the molecule in the charge exchange collision. Breakdown patterns for cyclobutane have also been calculated using the quasi-equilibrium theory (QET). Good agreement between the computed and experimental ion intensities was obtained for the primary dissociation processes. The relatively large C2H4+ intensity observed experimentally at higher energies is realized in the calculated spectra by assuming that direct cleavage of the C4H8+ ion occurs via a ``loose'' transition state, without prior isomerization. The results suggest that the previously reported differences in the 70-eV mass spectra of the C4H8 isomers are due in part to differences in the breakdown curves of the isomers.