Accurate rest frequencies for the submillimetre-wave lines of the  -containing isotopologues of and

Abstract
The submillimetre-wave spectrum of the molecular ions N¹⁵NH⁺, ¹⁵NNH⁺, N¹⁵ND⁺, and ¹⁵NND⁺ have been investigated in the laboratory using a source-modulation microwave spectrometer equipped with a negative glow discharge cell. The diazenylium ion was produced in a Ar/N₂/H₂(D₂) discharge plasma and the ¹⁵N-containing isotopologues were observed in natural abundance. Six new rotational transitions for the protonated species and seven for the deuterated ones were accurately measured in the frequency range 270-760 GHz. These new laboratory measurements of the rare isotopologues of N₂H⁺ provide very precise rest frequencies at millimetre and submillimetre wavelengths useful for the radioastronomical identification of their rotational lines in the ISM.

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