Methanimine, H2CNH, had been identified first in spectra
recorded toward Sgr B2 by
P. D. Godfrey, R. D. Brown, B. J. Robinson, and M. W. Sinclair,
Discovery of Interstellar Methanimine (Formaldimine)
Astrophys. Lett. 13, 119121 (1973).
Even though only one transition, 110 111 near 5290 MHz, was observed the detectionwas quite secure because of the 14N hyperfine pattern.
Methanimine turned out to be an abundant molecule not only in Sgr B2,
but also in other hot core sources; e.g.:
J. E. Dickens, W. M. Irvine, C. H. De Vries, and M. Ohishi,
Hydrogenation of Interstellar Molecules: A Survey for Methylenimine (CH2NH)
Astrophys. J. 479, 307312 (1997).
It was seen in absorption toward the dark cloud L183 and in emission
in one of three translucent clouds (CB 17):
B. E. Turner, R. Terzieva, and E. Herbst,
The Physics and Chemistry of Small Translucent Molecular Clouds. XII. More Complex Species Explainable by Gas-Phase Processes
Astrophys. J. 518, 699732 (1999).
The detection of the 13C isotopic species was reported in:
S.E. Cummins, R.A. Linke, and P. Thaddeus,
A Survey of the Millimeter-Wave Spectrum of Sagittarius B2
Astrophys. J. Suppl. Ser. 60, 819878 (1986).