Infrared photodissociation of cold CH₃⁺–He₂ complexes

ABSTRACT

A cryogenic 22-pole ion trap apparatus is used to probe weakly bound cold CH${}_3^{+}$–He${}_2$ complexes by IR action spectroscopy at 4 K. The infrared photodissociation spectrum of the antisymmetric C–H stretching vibration ${\nu }_3$ is recorded in the range of 3102–3139 cm⁻¹. A comparison between the experimental spectrum and a symmetric rotor Hamiltonian indicates that this band is strongly perturbed, but we report here a preliminary set of spectroscopic parameters.

GRAPHICAL ABSTRACT

KEYWORDS:

• Predissociation
• vibrational spectroscopy
• ion-helium complex
• ion trap
• CH${}_3^{+}$
• cold chemistry

Acknowledgements

We dedicate this work of unconventional spectroscopy of a weakly bound molecular complex to Dieter Cremer who always was fond of new scientific ideas and approaches to tackle the unexpected.

Disclosure statement

No potential conflict of interest was reported by the authors.

Note added in proof

Recently, Rauhut and coworkers calculated the potential energy surface, vibrational frequencies, and bond lengths of CH${}_3^{+}$–He. The work was submitted to J. Chem. Phys.

ORCID

Philipp C. Schmid http://orcid.org/0000-0002-1644-0495

Hiroshi Kohguchi http://orcid.org/0000-0001-9684-1258

Stephan Schlemmer http://orcid.org/0000-0002-1421-7281

Oskar Asvany http://orcid.org/0000-0003-2995-0803

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft (DFG) via grants AS 319/2-2 and SCHL 341/6 as wells as grant SCHL 341/15-1 (‘Cologne Center for Terahertz Spectroscopy’). H.K. is supported by the Yamada Science Foundation and Japan Society for the Promotion of Science - JSPS KAKENHI Grant No. 15KT0065.