Double resonance rotational spectroscopy of CH₂D⁺

I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
e-mail: asvany@ph1.uni-koeln.de

Received: 1 June 2016
Accepted: 16 August 2016

Abstract

Context. Deuterated forms of CH₃⁺ are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH₂D⁺ in space to date.

Aims. Four submillimetre rotational lines of CH₂D⁺ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection.

Methods. We used a low-temperature ion trap and applied a novel IR–mm-wave double resonance method to measure the rotational lines of CH₂D⁺.

Results. We measured 21 low-lying (J ≤ 4) rotational transitions of CH₂D⁺ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.