Evidence for Penning Ionization in the Generation of Electronically Excited States of Transition Metal Cations by Laser Vaporization

Abstract

We report the first evidence for the involvement of Penning ionization in the production of electronically excited state transition metal ions by laser vaporization in the presence of argon carrier gas. The use of argon as a carrier gas has been usually considered to be a more efficient cooling and quenching gas of the excited-state species. The current results show that this view is no longer valid and under certain conditions, where metastable argon atoms can be generated through the laser plasma vaporization, efficient production of electronic excited states of transition metal ions can result. The effect of Penning ionization is demonstrated for the production of excited states of Ni+, Nb+, and Pt+ ions through the coupling of the laser vaporization/ionization of metals and the mass-selected ion mobility techniques. The current finding has significant implications not only for understanding the mechanisms of ion production by laser-surface interactions, but also for developing new approaches to study state selected ion−molecule reactions.