Laboratory rotational ground state transitions of NH3D+ and CF+
1 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
2 Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
Received: 12 June 2016
Accepted: 7 July 2016
Aims. This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+.
Methods. Spectra in the millimetre-wave band were recorded by the method of rotational state-selective attachment of He atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH3D+ (JK = 10−00), and the two hyperfine components of the ground state transition of CF+ (J = 1−0) were measured with a relative precision better than 10-7.
Results. For both target ions, the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH3D+ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF+ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations and the intrinsic spectroscopic nature of a double-peaked line profile observed in the J = 1−0 transition towards the Horsehead photon-dominated region (PDR).
Key words: astrochemistry / ISM: molecules / methods: laboratory: molecular / line: identification / molecular data
© ESO, 2016