B. E. Turner and J. Bally
reported on the
Detection of Interstellar PN The First Identified Phosphorus Compound in the Interstellar Medium
Astron. Astrophys. 321, L75L79 (1987).
The J = 2 1, 3 2, and 5  4; transitions were detected with the NRAO 12 m and BTL 7 m telescopes in emission near 94.0, 141.0, and 234.9 GHz. The lines were detected in the high-mass star-forming regions Orion KL, W51M, and Sgr B2.
L. M. Ziurys, S. N. Milam, A. J. Apponi, and N. J. Woolf
Chemical Complexity in the Winds of the Oxygen-rich Supergiant Star VY Canis Majoris
Nature 447, 10941097 (2007).
PN was identified in the course of a molecular line survey with the ARO 12 m and the SMT 10 m telescopes, covering large sections of the 75270 GHz region.
S. N. Milam, D. T. Halfen, E. D. Tenenbaum, A. J. Apponi, N. J. Woolf,
and L. M. Ziurys
Constraining Phosphorus Chemistry in Carbon- and Oxygen-Rich Circumstellar Envelopes: Observations of PN, HCP, and CP
Astrophys. J. 684, 618625 (2008).
Several lines of PN were detected with the same instruments as above toward the envelopes of the carbon-rich late-type stars V1610 Cygni (aka CRL 2688) and CW Leonis (aka IRC +10216).
PN was also detected around a (low-mass) class 0 proto-star:
Detection of Phosphorus Nitride in the Lynds 1157 B1 Shocked Region
by T. Yamaguchi, S. Takano, N. Sakai, T. Sakai, S.-Y. Liu, Y.-N. Su, N. Hirano, S. Takakuwa, Y. Aikawa, H. Nomura, and S. Yamamoto,
Publ. Astron. Soc. Japan 63, L37L41 (2011).
The J = 2 1 transition near 94.0 GHz was detected in emission with the Nobeyama 45 m telescope in the course of a molecular line survey covering the 3 mm region.