The Absence of Interstellar HCCO and the Bates Dissociative Recombination Theory

A sensitive search for the ketyl radical, HCCO, in several interstellar sources has given upper limits for its column density of 4 x 10 to the 10th/sq cm in TMC 1 and 4 x 10 to the 12th/sq cm in Sgr B2. In conjunction with upper limits of 1.5 x 10 to the 12th/sq cm for the CCO radical, and the presence of ketene (H2CCO) at column densities of 2 x 10 to the 12th in TMC 1 and 1.7 x 10 to the 14th/sq cm in Sgr B2, an upper limit HCCO/H2CCDO not greater than 0.02 hence, it is deduced that dissociative electron recombination of H3C2O(+) produces ketene but not HCCO or CCO. This is in accord with the theory of Bates (1986) that only one H atom is likely to be detached by dissociative electron recombination with a polyatomic ion.