Letter to the Editor

Rotational transitions of CH₂D⁺ determined by high-resolution IR spectroscopy

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

Received: 28 April 2010
Accepted: 10 May 2010

Abstract

Context. Deuterated forms of CH are responsible for deuterium fractionation in warmer environments. Current searches for CH₂D⁺ are hampered by a lack of accurate laboratory data.

Aims. We demonstrate that IR spectroscopy at very high resolution can make accurate rotational predictions.

Methods. By combining a low-temperature ion trap with a narrow-bandwidth IR light source, we are able to measure vibrational transitions with high accuracy. A subsequent fit using an asymmetric rotor model allows predictions of MHz accuracy or even better.

Results. We predict rotational transitions up to 1.5 THz.