Carbon in Comet Bradfield 1979l

Abstract

Ultraviolet spectra of comet Bradfield obtained with IUE show a surprising absence of CO(+) despite the presence of CO2(+), and they also show, for the first time, the unambiguous presence of the Mulliken bands of C2. With the use of simultaneous ground-based data, a value of 0.00001 is derived for the transition moment of the a 3 Pi-X 1 Sigma g + transition of C2. The anomalous CO(+)/CO2(+) ratio can be accounted for by the different scale lengths of the species rather than by an abundance difference. Using the model of Feldman (1978), the upper limit for CO(+) is found to be consistent with the observed abundance of CO. On that same model, however, CO cannot produce nearly as much atomic carbon as is observed.