THE PURE ROTATIONAL SPECTRUM OF THE CoS RADICAL (X$^{4}\Delta_i$): CONTINUED STUDIES IN MONO-LIGATED COBALT SPECIES

Author Institution: Department of Chemistry, Department of Astronomy, Steward Obsevatory, University of Arizona, Tucson, AZ 85721The sub-millimeter wave spectrum of the CoS radical has been observed in the frequency range 350-540 GHz using direct absorption techniques. This work is the first spectroscopic study of this molecule. Cobalt vapor was reacted with CS$_{2}$ to produce CoS. Rotational transitions from three spin-components in the radical's X $^{4}\Delta _{i}$ ground state have been recorded thus far, and magnetic hyperfine splittings due to the $^{59}$Co nucleus (I = 7/2) have been resolved. We are continuing our search to identify the fourth spin-component. Transitions from the Co$^{34}$S isotopomer were also measured, as well as several arising from excited vibrational levels. There is no evidence of $\lambda $ -doubling in the lower three spin-components ($\Omega $ = 7/2, 5/2, 3/2). The hyperfine pattern in the various spin-orbit components is somewhat irregular, particularly the $\Omega $ = 3/2, suggesting some mixing from nearby excited electronic states. The preliminary data have been fit with a case (a) Hamiltonian, and spectroscopic constants have been determined. The most current results of this study will be presented