Molecular dynamics mass spectrometric study of the collision-induced dissociation of CS 2+ ions at low and intermediate collision energies

Abstract

The dynamics of the collision-induced dissociation of CS 2 + molecular ions to CS and S + fragment ions has been investigated using a crossed-beam tandem hybrid mass spectrometer at collision energies ranging from near threshold to 34.5 eV in the center-of-mass (CM) reference frame. The results show that small impact parameter impulsive collisions are involved in the collisional activation process, resulting in extensive scattering of fragment ions with intensity maxima at non-zero angles. The dissociation of CS 2 + to S + proceeds via a mechanism mainly involving the transfer of the minimum amount of energy required to dissociate the parent ion into S + ( 4S) and CS (X 1 Σ +) at all collision energies. However, the mechanism for the formation of CS + depends strongly on the collision energy. Energy transfer is very efficient for this process and a large fraction of the CM collision energy is converted to internal excitation of the colliding CS 2 + ions up to a maximum of nearly 16 eV (at 34.5 eV collision energy). At the lowest collision energy we have investigated, 6.5 eV, the lowest energy reaction path to form CS + (X 2 Σ +) and S ( 3P) is followed exclusively. However, as the collision energy is increased, several additional dissociation channels contribute towards the total dissociation. These results are rationalized by the efficient electronic excitation of the colliding CS 2 + ions at these collision energies.