Dispersed-fluorescence spectroscopy of jet-cooled calcium ethoxide radical (CaOC2H5)

Abstract

Metal-containing free radicals are important intermediates in metal-surface reactions and in the interaction between metals and organic molecules. In the present work, dispersed fluorescence (DF) spectra of the calcium ethoxide radical (CaOC$_2$H$_5$) have been obtained by pumping the ${\tilde A^2}{\rm{A}}' \leftarrow {\tilde X^2}{\rm{A}}'$ and the ${\tilde B^2}{\rm{A}}'' \leftarrow {\tilde X^2}{\rm{A}}'$ origin bands in its laser-induced fluorescence (LIF) spectrum. CaOC$_2$H$_5$ radicals were produced by 1064 nm laser ablation of calcium grains in the presence of ethanol under jet-cooled conditions. Dominant transitions in the vibrationally resolved DF spectra are well reproduced using Franck-Condon factors predicted by complete active space self-consistent (CASSCF) calculations. Differences in transition intensities between the ${\tilde A^2}{\rm{A}}' \rightarrow {\tilde X^2}{\rm{A}}'$ and the ${\tilde B^2}{\rm{A}}'' \rightarrow {\tilde X^2}{\rm{A}}'$ DF spectra are attributed to the pseudo-Jahn-Teller interaction between the $\tilde A ^2 \rm{A}'$ and the $\tilde B ^2 \rm{A}''$ states. Collision-induced population transfer between these two excited electronic states results in additional peaks in the DF spectra.