Abstract
The collision-induced dissociation (CID) dynamics of the Ar2++Ar collision system are investigated at different Ar2+ internal energy distributions in a guided-ion beam (GIB) apparatus. The internal energy of reactant ions, assumed vibrational in a first approximation, is controlled by varying the position of ionization in a supersonic jet, electron impact ion source. Three conditions are investigated: cold, in which the ions are produced as vibrationally relaxed as possible; intermediate, in which a substantial shift in the CID onset is observed; hot, in which the apparent CID threshold is at near thermal collision energies. The vibrational distribution of the Ar2+ ions is probed at the same conditions by measuring the kinetic energy release of photofragment Ar+ following Σg+2←Σu+2 photodissociation. The derived internal energy distributions are then used to model the observed CID cross sections with a modified line-of-centers approach to assess vibrational effects in the single-collision cross sections. The intermediate CID cross sections are consistent with a negligible vibrational enhancement beyond the statistical predictions. A substantial increase in cross section is observed when going from intermediate to hot conditions, despite a weak increase in internal energy, as apparent from the photodissociation measurements. Contributions from metastable states, not registered in the photodissociation experiment, can explain this disparity.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call