Quantum state control on the chemical reactivity of a transition metal vanadium cation in carbon dioxide activation.

Abstract

By combining a newly developed two-color laser pulsed field ionization-photoion (PFI-PI) source and a double-quadrupole-double-octopole (DQDO) mass spectrometer, we investigated the integral cross sections (σs) of the vanadium cation (V+) toward the activation of CO2 in the center-of-mass kinetic energy (Ecm) range from 0.1 to 10.0 eV. Here, V+ was prepared in single spin-orbit levels of its lowest electronic states, a5DJ (J = 0-4), a5FJ (J = 1-5), and a3FJ (J = 2-4), with well-defined kinetic energies. For both product channels VO+ + CO and VCO+ + O identified, V+(a3F2,3) is found to be greatly more reactive than V+(a5D0,2) and V+(a5F1,2), suggesting that the V+ + CO2 reaction system mainly proceeds via a "weak quintet-to-triplet spin-crossing" mechanism favoring the conservation of total electron spins. In addition, no J-state dependence was observed. The distinctive structures of the quantum electronic state selected integral cross sections observed as a function of Ecm and the electronic state of the V+ ion indicate that the difference in the chemical reactivity of the title reaction originated from the quantum-state instead of energy effects. Furthermore, this work suggests that the selection of the quantum electronic states a3FJ (J = 2-4) of the transition metal V+ ion can greatly enhance the efficiency of CO2 activation.