INTERSYSTEM TRANSITIONS OF INTERSTELLAR CARBON-MONOXIDE TOWARD ZETA-OPHIUCHI

Absorption from seven intersystem (triplet-singlet) transitions of int erstellar (CO)-C-12 were detected in ultraviolet spectra of zeta Oph. The observed equivalent widths are approximately consistent with the t ransitions' predicted f-values (Morton & Noreau 1994) and the (CO)-C-1 2 column density derived from the weakest of the observed A-X bands. T hese unsaturated intersystem transitions provide the opportunity to me asure the (CO)-C-12 column density for heavily reddened (dense) sight lines. Laboratory measurements of oscillator strengths more precise th an available ones will be needed to derive accurate column densities.