Absolute rate constants for the reaction of atomic hydrogen with ketene from 298 to 500 K

Abstract

Rate constants for the reaction of atomic hydrogen with ketene have been measured at room temperature by two techniques, flash photolysis–resonance fluorescence (FP–RF) and discharge flow–resonance fluorescence (DP–RF). The measured values are (6.19±1.68) ×10−14 and (7.3±1.3) ×10−14 cm3 molecule−1 s−1, respectively. In addition rate constants as a function of temperature have been measured over the temperature range 298–500 K by the FP–RF technique. The results are best represented by the Arrhenius expression k= (1.88±1.12) ×10−11 exp(−1725±190/T) cm3 molecule−1 s−1, where the indicated errors are at the two standard deviation level. These results are compared to two previous investigations both of which employed the discharge flow–mass spectrometric technique. Also they are compared to the analogous reaction, H+C2H4 (high pressure limit) since both reactions refer to addition across a carbon–carbon double bond. The reaction is considered theoretically from the activated complex point of view. Lastly, the suggestion that this reaction could contribute to the destruction of ketene in interstellar clouds is evaluated based on the present results.