Terahertz spectroscopy of the ¹⁵NH₂ amidogen radical^⋆

¹ Univ. Lille, CNRS, UMR 8523 – PhLAM – Physique des Lasers, Atomes et Molécules, 59000 Lille, France
e-mail: laurent.margules@univ-lille1.fr
² SOLEIL Synchrotron, AILES beamline, l’Orme des Merisiers, Saint-Aubin, 91192 Gif-sur-Yvette Cedex, France
³ Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
⁴ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, 92190 Meudon, France
⁵ LERMA, UMR 8112 CNRS, 24 Rue Lhomond, 75231 Paris Cedex 05, France

Received: 27 January 2016
Accepted: 31 March 2016

Abstract

Context. The determination of isotopic ratios in interstellar molecules is a powerful probe of chemical routes leading to their formation. In particular, the ¹⁴N/¹⁵N abundance ratio of nitrogen-bearing species provides information on possible fractionation mechanisms. Up to now there is no accurate determination of this ratio in the interstellar medium (ISM) for the amidogen radical, NH₂.

Aims. This work is aimed at determining rotational frequencies of ¹⁵NH₂ to enable its astronomical detection, which will help to understand the formation mechanisms of nitrogen hydrides in the ISM.

Methods. We performed complementary measurements using both synchrotron-based, broadband far-infrared and high-resolution, submillimeter-wave frequencies to investigate the pure rotational spectrum of the ¹⁵NH₂ species.

Results. The first spectroscopic study of the ¹⁵N-isotopologue of the amidogen radical yielded an accurate set of molecular parameters.

Conclusions. Accurate frequencies are now available for ¹⁵NH₂ up to 7 THz (with N′′ ≤ 13) allowing dedicated astronomical searches to be undertaken.