Propargylimine in laboratory and in space

We have searched for propargylimine at 3 and 2mm in the spectral survey of the quiescent giant molecular cloud G+0.693-0.027 located in the "Central Molecular Zone", close to the Galactic Centre. About 1000 rotational transitions have been recorded for the E- and Z-propargylimine, in the laboratory. These new data have enabled the determination of a very accurate set of spectroscopic parameters including rotational, quartic and sextic centrifugal distortion constants.

The improved spectral data allow us to perform a successful search for this new imine in the G+0.693-0.027 molecular cloud. Eighteen lines of Z-propargylimine have been detected at level >2.5*sigma, resulting in a column density estimate of N=(0.24+/-0.02)x10^-14^cm^-2^. An upper limit was retrieved for the higher-energy E isomer, which was not detected in the data.

The fractional abundance (w.r.t. H_2_) derived for Z-propargylimine is 1.8x10^-10^. We discuss the possible formation routes by comparing the derived abundance with those measured in the source for possible chemical precursors.