Collision energy effects in tanden mass spectrometry as revealed by a proton‐bound dimer ion

Abstract

AbstractMass spectra resulting from collision‐induced decomposition of the proton‐bound dimer of iso‐propylamine and sec‐butylamine have been obtained as a function of laboratory collision energy over the range 10‐6000 eV. The ratio of the two principal fragment ions from the dimer ion measured as a function of collision energy is compared with the ratio expected as a function of internal energy as calcualted based on the statistical theory of mass spectra. This comparison indicates that the average energy deposited into the dimer ion upon collision reaches a maximum at a collision energy of ∼70 eV. The average internal energy of the ions at this collision energy is ∼4.3 eV. Other fragment ions which arise from higher energy decompositions are also observed in the spectra at much lower intensities. The relative intensities of these fragments indicate that the probability for large energy transfers are highest at ke V collision energies. These observations are interpreted on the basis of differences in the postcollision internal energy distributions resulting from keV and eV collisions.