Terahertz spectroscopy and global analysis of the rotational spectrum of doubly deuterated Amidogen radical ND\(_{2}\)

Abstract

The deuteration mechanism of molecules in the interstellar medium (ISM) is still being debated. Observations of deuterium-bearing species in several astronomical sources represent a powerful tool to improve our understanding of the interstellar chemistry. The doubly deuterated form of the astrophysically interesting Amidogen radical could be a target of detection in space. In this work, the rotational spectrum of the ND\(_{2}\) radical in its ground vibrational and electronic \(X^{2}B_{1}\) states has been investigated between 588 and 1131 GHz using a frequency modulation millimeter/submillimeter-wave spectrometer. The ND\(_{2}\) has been produced in a free-space glass absorption cell by discharging a mixture of ND\(_{3}\) and Ar. Sixty-four new transition frequencies involving \(J\) values from 2 to 5 and \(K_{a}\) values from 0 to 4 have been measured. A global analysis including all the previous field-free pure rotational data has been performed, allowing for a more precise determination of a very large number of spectroscopic parameters. Accurate predictions of rotational transition frequencies of ND\(_{2}\) are now available from a few GHz up to several THz.