Electronic absorptions of C5+ detected in the visible through action spectroscopy in a cryogenic trap

Abstract

The ${}^2{\mathrm{\Pi }}_g\leftarrow X{}^2{\mathrm{\Sigma }}_u^{+}$ electronic spectrum of C ${}_5^{+}$ in the gas-phase with origin band at $513\mathrm{nm}$ is reported following experiments in a cryogenic ion trapping instrument. Buffer gas-cooled C ${}_5^{+}$ ions, generated by laser vaporisation of graphite, were investigated using two action spectroscopy approaches. Laser-induced dissociation of weakly bound ${\mathrm{C}}_5^{+}-{\mathrm{He}}_n$ complexes synthesised in the trap reveal a linear dependence of the absorption energies on n allowing prediction of those of the bare ion C ${}_5^{+}$. These results are confirmed in two colour experiments on C ${}_5^{+}$, by monitoring fragmentation into the ${\mathrm{C}}_3^{+}+{\mathrm{C}}_2$ product channel. The data are supplemented with high-level electronic structure calculations which support the assignment of $D_{\mathrm{\infty }h}$ symmetry to the ground electronic state. These laboratory results provide the requisite data needed for spectroscopic detection of this structure in terrestrial and extraterrestrial environments. GRAPHICAL ABSTRACT