CAN GAS-PHASE RADICAL/NEUTRAL REACTIONS ACCOUNT FOR OBSERVED ABUNDANCES OF PROPYNAL WITHIN DENSE INTERSTELLAR CLOUDS?

摘要

Recent studies have suggested that the commonly accepted pathway to propynal formation within dense interstellar (IS) clouds, namely, the radiative association of C_2H_3~+ with CO, is incapable of yielding propynal upon dissociative recombination. We propose here that the reaction of C_2H + H_2CO can account for propynal's presence within TMC-1 and Sgr B2. Ab initio calculations for the C_3H_3O potential energy surface yield information on possible product channels for the reaction of C_2H with H_2CO. Formation of propynal + H is expected to be a major product channel for this reaction. Implications for the IS occurrence of pentadiynal (HCCCCCHO) are also presented.