J. Phys. Chem. 1984,88, 6009-6014 spectrometry to detect 0 and HCO and 0 and H, respectively. These authors have observed that the formation of HCO and H is roughly equally likely at 1-4 mbar in their flow systems. For C3H6and 1-C4Hs, we see (Table 111) that the threshold energies for substitution are more than 2.5 times larger than the measured activation energies at low temperatures. A simple explanation for this difference is given by a second reaction channel having a low activation energy. It is unlikely that this additional reaction path results in abstraction of an H atom since the threshold energies are even higher for abstraction than for substitution (Table 111). Hence, addition of 0 atoms to the double
6009
bond as it has been proposed previously2 most likely presents the additional reaction channel. Acknowledgment. Financial support of the Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie is gratefully acknowledged. Some equipment was provided by the UBA Project No. 10.402.421. We thank Dr. C. Zetzsch for valuable discussions, Dr. R. D. Kenner for helpful suggestions during the preparation of the manuscript, and Dr. R. A. Perry, Dr. D. L. Singleton, and Prof. Dr. H. Gg. Wagner for providing preprints of their work. Registry No. 0, 17778-80-2; C2H4,74-85-1; C,H6, 115-07-1; 1-C4H,, 106-98-9; NO, 10102-43-9.
(39) Dransfeld, P.; Wagner, H. Gg., private communication.
Formation of Vibrationally Excited COT in OCS Photolysis Jeffrey A. Joens and Edward J. Bair* Department of Chemistry, Indiana University, Bloomington, Indiana 47405 (Received: May 2, 1984)
Measurements of the vibrational excitation following flash photolysis of OCS are reported in which the extent of vibrational excitation of the COTproduct is inferred from changes in the vibronic continuum of OCS, which acts as a sink for excess vibrational energy in this system. The excitation resulting from primary photolysis is distinguished from that resulting from the reaction of S('D) with OCS using gas mixtures which deactivate S('D) in varying degrees. The average quantum states of the COT product are as follows: OCS hv S('D) Cot, u1 < 0.25; OCS S(lD) S,('A) COT, u2 = 2.7 f 0.5. The experiment yields total cross sections for removing S('D) by various gases within the uncertainties of the values in the literature, that is Ar 0.01 1 f 0.003, N2 0.059 0.015, O2 0.066 f 0.022, He
