GROUND STATE OF THE $C_{6}$ MOLECULE

$^{1}$ W. R. M. Graham, K. I. Dismuke, and W. Weltner, Jr., Astrophys. J. 204, 301 (1976). $^{2}$ K. Raghovachari, R. A. Whiteside, and J. A. Pople, J. Chem. Phys. 85, 6623 (1986). $^{3}$ D. W. Ewing (private communication).Author Institution: Department of Chemistry, University of Florida; Department of Chemistry, Wake Forest University; Nicols Research Corp., Wake Forest UniversityPure carbon molecules have been trapped in neon and argon matrices at $4^{\circ}K$ from the vapor over thermal- or laser-heated graphite or from the microwave discharge of traiacetylene in argon. Linear triplet $C_{4}$ has previously been identified.1 Corresponding signals attributed to a linear $C_{6}$ molecule in a $3\Sigma$ state, probably the ground state, are also observed. $^{13}C$ nuclear hyperfine structure again supports a cumulene-type bonding. The zero-field-splitting parameter was found to be $|p| = 0,363 cm^{-1}$ (in neon), about $50^{\circ}$ larger than that of $C_{4}$. These results will be discussed relative to recent ab initio $calculations.^{2,3}