Quantum-state-specific reaction rate measurements for the photo-induced reaction Ca^+ + O2 -> CaO^+ + O

Author
Abstract
Atoms and molecules often react at different rates depending on their internal quantum states. Thus, controlling which internal states are populated can be used to manipulate the reactivity and can lead to a more detailed understanding of reaction mechanisms. We demonstrate this control of reactions by studying the electronically excited state reaction Ca<sup>+</sup> + O<sub>2</sub> \textrightarrow CaO<sup>+</sup> + O. This reaction is exothermic only if Ca<sup>+</sup> is in one of its excited electronic states. Using laser-cooling and electrodynamic trapping, we cool and trap Ca<sup>+</sup> at millikelvin temperatures for several minutes. We can then change the fraction of time they spend in each of the two excited states by adjusting the detunings of the cooling lasers. This allows us to disentangle the reactions that begin with Ca<sup>+</sup> in the <sup>2</sup>P<sub>1/2</sub>-state from the ones where Ca<sup>+</sup> is in the <sup>2</sup>D<sub>3/2</sub>-state. Using time-of-flight mass spectrometry, we determine independent reaction rate constants for Ca<sup>+</sup> in both electronically excited states.
Year of Publication
2019
Journal
Molecular Physics
Number of Pages
1-7
Date Published
2019-05
ISSN Number
0026-8976
URL
https://www.tandfonline.com/doi/full/10.1080/00268976.2019.1622811
DOI
10.1080/00268976.2019.1622811
JILA PI
Journal Article