Ultrafast ionization and subsequent coulomb explosion of zirconium oxide and tungsten carbide “superatomic” cluster species and comparison to group 10 metals

Abstract

Ultrafast pulses centered at 624 nm are used to explore the ionization behavior of small zirconium oxide, palladium oxide, tungsten carbide, and platinum clusters. Zr_xO_y and W_xC_y have been identified as “superatom” species as they are isovalent with Pd_xO_y and Pt_xC_y clusters, respectively. Intensity selective scanning (ISS) technique is used to study the high charge states of each metal as a function of laser intensity. The ion signals of each atomic charge state are compared to those predicted from semi-classical atomic tunneling theory using sequential ionization potentials. A clear difference in ion signal appearance potentials is observed in early-group transition metal clusters vs. late transition metal clusters, indicating the significance of the d-orbitals in the overall ionization behavior of these clusters. The ionization behavior of each cluster species is explored in the context of transition metal clusters.