Submillimeter-wave spectrum of aminoacetonitrile and its deuterated isotopologues, possible precursors of the simplest amino acid glycine

Aminoacetonitrile, CH₂NH₂CN, has been considered one of the important precursors of glycine, the simplest amino acid, and was identified in Sgr B2(N) by Belloche et al. based on their reanalysis of previous laboratory measurements. However, these laboratory measurements were limited to the 1 mm wavelength region even for the normal species, and recent new radio telescopes like ALMA require rest frequencies in a higher frequency range. Therefore, we have extended the pure rotational spectra of aminoacetonitrile and its amino-hydrogen-deuterated isotopologues (NHDCH₂CN and ND ₂CH₂CN) up to 1.2 THz and 0.6 THz, respectively. Belloche et al. indicated that the normal species may have been misassigned in a previous microwave study by Bogey et al. We found that two more b-type spectral transitions were misassigned, and all b-type transition frequencies above K _a = 2 had to be remeasured. For isotopologues, spectra above 40 GHz were observed for the first time and higher order centrifugal distortion constants have been determined. The extension of the measurements helped improve the molecular constants. The errors in the frequency catalog data of normal and deuterated isotopologues are on the order of 100 kHz up to 1.2 THz and 0.6 THz, respectively, which are precise enough for the future astronomical observations.