DETERMINATION OF THE GEOMETRIC STRUCTURE OF BUTATRIENYLIDENE, $H_{2}CCCC$, AND OF THE HYPERFINE STRUCTURE OF PROPYNONYL, HCCCO

Author Institution: Department of Chemistry, Wesleyan University; Harvard-Smithsonian Center for Astrophysics, Wesleyan University; Harvard-Smithsonian Center for Astrophysics, Wesleyan University; Division of Applied Sciences, Harvard University; Department of Chemnistry, University of MississippiThe microwave spectra of the N = 1 - 0 and 2 -1 transitions of six isotopic species of the singlet carbene butatrienylidene ($H_{2}CCCC,H_{2}CCC^{13}C, H_{2}CC^{13}CC, H_{2}C^{13}CCC, H_{2}^{13}CCCC, D_{2}CCCC$) were measured with a Fourier transform microwave spectrometer and the $r_{0}$ and $r_{1}$ structures were determined. Both structures agree well with the calculated ab initio structure indicating that the carbon chain backbone is cumulenic, In addition, the two lowest hyperfine split transitions of HCCCO (N = 1 - 0 and 2 -1) have been measured with a Fourier transform microwave spectrometer. The frequencies, accurate to better than 0.20 km/s, should help guide future searches for interstellar HCCCO