1-propanimine measured freq. and residuals

The new prediction allowed us to search for 1-propanimine toward the high-mass star forming region Sagittarius B2(N), the dark molecular cloud TMC-1, as well as a sample of low-mass protostellar objects. These sources were observed with the Atacama Large Millimeter/submillimeter Array, the Green Bank Telescope, or the IRAM 30m telescope. A total of 585 and 296 transitions of the E and Z-1-propanimine, respectively, were newly assigned and fitted in the laboratory spectra recorded up to 470GHz.

Quantum numbers up to J=73 and Ka=18 were reached for the E isomer and J=56 and Ka=17 for the Z isomer. We report the nondetection of 1-propanimine toward all astronomical sources investigated in this work. We find in particular that 1-propanimine is at least 20 times less abundant than methanimine in the envelope of the high-mass star forming region Sagittarius B2(N).

The accurate spectroscopic prediction of its spectrum provided in this work will allow astronomers to continue the search for 1-propanimine in the ISM.