PNNL

Abstract

The reactions of lanthanide cations (Ln+ = Ce+, Pr+, Nd+ - Eu+) and actinide cations (An+ = Th+, U+ - Am+) with CO2 were studied by tandem inductively coupled plasma mass spectrometry and the absolute reaction cross sections as a function of kinetic energy were determined. The reaction efficiency (k/kcol) where the collision limit of the observed barrierless exothermic reactions is correlated to the promotion energy (Ep) to the first excited state with two free d-electrons, and barriers in excess of the reactants’ energy are observed for metal cations with a sufficiently high Ep. The Ep likely helps set the energy between the crossing of the ground and excited (reactive) potential energy surface that then sets the reaction rate. The Ep appears to have a more significant effect on the reaction rate than any spin-restrictions introduced by the neutral reactant (CO2) and product (CO).