Laboratory observation of para-H2C4N

The rotational spectrum of para-H2C4N (I(H) = 0) in the K-a = 1 rotational level has been observed in supersonic expansion at low temperature by Fourier transform microwave spectroscopy. The C-2v structure of H2C4N has been confirmed by an analysis of both the present K-a=1 transitions and the K-a=0 transitions from the previous ortho-H2C4N(I(H) = 1 study. Rest transition frequencies of para-H2C4N are now available for radio-astronomical searching.