Rotational state-dependent attachment of He atoms to cold molecular ions: An action spectroscopic scheme for rotational spectroscopy

• Published in: Journal of molecular spectroscopy Vol. 332; pp. 67 - 78
• Main Authors: Brünken, Sandra, Kluge, Lars, Stoffels, Alexander, Pérez-Ríos, Jesús, Schlemmer, Stephan
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-02-2017
• Subjects: Action spectroscopy; Cryogenic ion trap; Rotational spectroscopy; Ternary association reactions; Ternary association reactions; Cryogenic ion trap; Rotational spectroscopy; Action spectroscopy
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1016/j.jms.2016.10.018

[Display omitted]
•Novel action spectroscopic scheme for rotational spectroscopy in cold ion traps.•Detailed kinetics model including key elementary processes tested on CD+.•Determination of rotational state-dependent ternary attachment rate coefficients.•Improved frequency accuracy of the CD+ (J=1–0) rotational ground state transition.•General applicability for high-resolution rotational spectroscopy of molecular ions.
We present a kinetics model description of a newly developed action spectroscopic method for rotational spectroscopy based on rotational state-dependent three-body attachment of He atoms to cold molecular ions stored in a cryogenic 22-pole ion trap. The model results from numerical simulations and an approximate analytical expression are compared to measurements of the J=1–0 rotational transition of CD+, for which we obtain a refined transition frequency of 453.5218509(7)GHz. From the analysis of the spectroscopic data recorded at varying experimental conditions, e.g. over a wide range of He number densities and excitation powers, we deduce that the ternary rate coefficient in the first excited rotational state of CD+ is reduced to (55±5)% of the rotational ground state value. This decrease in the rate coefficient can be rationalized as an increase of the redissociation probability in the ternary collision process. A summary of rotational spectroscopy measurements of other molecular ions using the new method will be given, and its general applicability is discussed.