Theoretical study of the butadiynyl and cyanoethynyl radicals: Support for the identification of C3N in IRC+10216

Quantum-mechanical calculations, using the matrix Hartee-Fock model, have been performed for the butadiynyl and cyanoethynyl radicals. A rotation constant, B/sub e/, of 4753 MHz is calculated for C4H while for C3N the value 4955 MHz is obtained. These may be compared with the rotation constant, B0, of 4947.5 MHz derived from the recently observed doublets in the millimeter-wave spectrum of IRC+10216, suggesting the cyanoethynyl radical as the carrier species of these lines. The electric dipole moment and hyperfine coupling constants of both species are predicted