The Microwave Spectrum of Vinyl Cyanide

The rotational spectrum of the slightly asymmetric top, vinyl cyanide, has been investigated in a microwave spectrograph employing Stark effect modulation and in a direct absorption cell. The rotational constants a = 49 076.2 Mc/sec, b = 4971.33, and c = 4514.05 were computed from the observed frequencies of the J = 2→3 transitions. From measurements of the Stark effect, the components of the dipole moment were found to be μa = 3.68D, μb = 1.25, μ = 3.89. Partial resolution of the hyperfine structure of certain lines gave the value —3.0 Mc/sec for the ξaa component of quadrupole coupling.