15min:
MICROWAVE SPECTROSCOPY OF TWO ISOELECTRONIC RADICALS:
2,4,6-HEPTATRIYNYL, H2C-CequivC-CequivC-CequivC-H, AND 2,4-HEXADIYNYLNITRILE, H2C-CequivC-CequivC-CequivN.

WEI CHEN, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; and Department of Chemistry, Wesleyan University, Middletown, CT 06459; STEWART E. NOVICK, Department of Chemistry, Wesleyan University, Middletown, CT 06459; M. C. MCCARTHY, P. THADDEUS, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138.

The isoelectronic pair of radicals 2,4,6-heptatriynyl, H2C-CequivC-CequivC-CequivC-H, and 2,4-hexadiynylnitrile, H2C-CequivC-CequivC-CequivN, were produced in a pulsed discharge supersonic jet and detected by Fourier transform microwave spectroscopy. Seven rotational transitions of the heptatriynyl radical from N' = 4 to 10 and six rotational transitions of the hexadiynylnitrile radical from N' = 4 to 9 in the Ka = 0 ladder were observed between 6 and 17 GHz. For each species, over 50 hyperfine components were measured and assigned with an uncertainty of 5 kHz. Precise rotational, centrifugal distortion, spin-rotation, and various hyperfine coupling constants were determined for both H2C7H and H2C6N.