Quantum Spin-Orbit Electronic State Selection of Atomic Transition Metal Vanadium Cation for Chemical Reactivity Studies.

By combining a pulsed laser ablation vanadium atom (V) beam source with the two-color laser sequential electric field pulse scheme for pulse field ionization-photoion (PFI-PI) detection, we have developed a quantum spin-orbit state selected transition metal ion source for ion-molecule reaction studies. As a demonstration, we show that the V ion can be prepared in the single spin-orbit levels of its three lowest quantum electronic states, V[aD ( J = 0-4), aF ( J = 1-5), and aF ( J = 2-4)], achieving laboratory kinetic energy ( E) resolutions of ≤0.2 eV. The precursor V atom beam is first excited to high- n Rydberg states by resonance-enhanced visible-ultraviolet laser photoexcitation via the V*[3d(F) 4s4p (P°)] neutral intermediate state. The total photon energy is tuned in the regions from 54 380 to 63 520 cm to cover the photoionization energies for the formation of these spin-orbit states. Sharp Rydberg transitions converging to the V[aD ( J = 1 and 2)] spin-orbit levels are identified in the respective PFI-PI spectra for the V[aD ( J = 0 and 1)] states. The analysis of these Rydberg members observed yields an ionization energy of 54 412.65 ± 0.15 cm for V atom, which is in excellent accord with the literature value of 54 413 ± 1 cm eV. In order to understand the profile for the PFI-PI spectrum of V ion observed and thus obtain reliable Stark shift corrections by using the sequential PFI-PI detection scheme, we have also examined the PFI-PI spectrum for Ar(P) in detail by varying the retarding as well as the PFI electric field pulses.