Laboratory and astronomical discovery of the cyanovinyl radical H₂CCCN

We report the first laboratory and interstellar detection of alpha-cyano vinyl radical (H2CCCN). This species was produced in by an electric discharge a gas mixture cyanide, CH2CHCN, Ne, its rotational spectrum characterized using Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating frequency region 8-40 GHz. The observed shows complex structure due to tunneling splittings between two torsional sublevels ground vibronic state, 0+ 0-, derived from large-amplitude inversion motion. In addition, presence equivalent hydrogen nuclei makes necessary discern ortho- para-H2CCCN. A least squares analysis reproduces transition frequencies with standard deviation ca. 3 kHz. Using predictions, this is detected cold dark cloud TMC-1 Yebes 40m telescope QUIJOTE line survey. 404-303 505-404 transitions, composed several hyperfine components, were 31.0-50.4 GHz range. Adopting temperature 6K we derive column density (1.4+/-0.2)e11 cm-2 (1.1+/-0.2)e11 for ortho-H2CCCN para-H2CCCN, respectively. reactions C + CH3CN, perhaps also N CH2CCH, emerge as most likely routes H2CCCN TMC-1.