Accurate Laboratory Measurement of the Complete Fine Structure of the N = 1 − 0 Transition of 15 NH

Abstract

The imidogen radical is an important molecule of the chemistry of nitrogen in the interstellar medium and is thought to be a key intermediate in the gas-phase synthesis of ammonia. The full fine structure of the rotational transition of has been observed for the first time by pure rotational spectroscopy around 1 THz. The radical has been produced by means of low-pressure glow discharge of H 2 and -enriched nitrogen. A number of hyperfine components have been observed and accurately measured. The analysis of the data provided very precise spectroscopic constants, which include rotational, centrifugal distortion, electron spin–spin interaction, and electron spin–rotation terms in addition to the hyperfine parameters relative to the isotropic and anisotropic electron spin–nuclear spin interactions for 15 N and H and to the nuclear spin–rotation for 15 N. The efficiency of the discharge system allowed us to observe several components of the same rotational transition in the excited vibrational state v  = 1, for which a set of spectroscopic constants has also been determined.