High-resolution spectroscopy of the ν₃ antisymmetric C–H stretch of C₂H₂⁺ using leak-out action spectroscopy

Abstract

The antisymmetric C–H stretching vibration ${\nu }_3$ (${}^2\mathrm{\Pi }\leftarrow {}^2\mathrm{\Pi }$) of ionised acetylene, ${\mathrm{C}}_2{\mathrm{H}}_2^{+}$, has been revisited using a cryogenic 22-pole ion trap machine. Two action spectroscopic techniques, the novel leak-out spectroscopy (LOS) method and the more established laser-induced reactions (LIR) method, are applied and compared. Mass selectivity and cryogenic temperatures down to 4 K enabled the observation of uncontaminated spectra in which the Λ-doubling components of this open-shell molecule are mostly well resolved, leading to a slight refinement of the spectroscopic parameters.

GRAPHICAL ABSTRACT

Keywords:

• Ion traps
• rovibrational spectroscopy
• action spectroscopy
• carbocations
• lambda doubling

Acknowledgments

The LIR-measurement of the Q-branch depicted in Figure 3 has been conducted in the year 2008 in collaboration with Sabrina Gärtner and Jürgen Krieg. Additional LIR measurements have been performed by Pavol Jusko in 2014 (not shown in this work).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The current work has been supported by an ERC advanced grant (MissIons: 101020583), the Deutsche Forschungsgemeinschaft (DFG) via SFB 956 (project ID 184018867), sub-project B2, and the Gerätezentrum “Cologne Center for Terahertz Spectroscopy” (SCHL 341/15-1). W.G.D.P.S. thanks the Alexander von Humboldt foundation for funding through a postdoctoral fellowship. The authors gratefully acknowledge the work done by the electrical and mechanical workshops of the I. Physikalisches Institut over the last years.