Knowledge Bank

We have recently detected the $CCH(X2\Sigma )$ radical by 193nm ArF excimer laser photolysys of acetylene. Over a hundred absorption peaks are observed in $1750-1900cm-1$ region and time profiles of all the absorption peaks show that the species are produced not instantaneously and decay in 10 micro seconds at the pressure of 100mTorr acetylene. When some buffer gas( $H2$ or $CH4$) is added, the time profiles change drastically and each peak shows its characteristic behavior, so that the ground state CCH lines are distinguished from many other lines by using this kinetic information. Molecular constants ($B\prime ,D\prime ,\gamma \prime$, and $\nu O$) of the $\nu 3$ band are detemined by fixing the ground state constants to a previous MW $result.1$ $\mathrm{<mrow\; data-mjx-texclass="ORD">1.</mrow>}$ K.V.L.Sastry et al., Astrophys.J. 251, L119 (1981)