Intersystem Transitions of Interstellar Carbon Monoxide toward zeta Ophiuchi
Federman, S. R.; Lambert, David L.; Cardelli, Jason A.; Sheffer, Yaron; Morton, D. C.
United States, Canada
Abstract
Absorption from seven intersystem (triplet-singlet) transitions of interstellar (12)CO were detected in ultraviolet spectra of zeta Oph. The observed equivalent widths are approximately consistent with the transitions' predicted f-values and the (12) CO column density derived from the weakest of the observed A-X bands. These unsaturated intersystem transitions provide the opportunity to measure the (12)CO column density for heavily reddened (dense) sight lines. Laboratory measurements of oscillator strengths more precise than available ones will be needed to derive accurate column densities.