A study of the intersystem crossing reaction induced in gaseous sulfur dioxide molecules by collisions with nitrogen and cyclohexane at 27°C

✍ Scribed by Abraham Horowitz; Jack G. Calvert

• Publisher: John Wiley and Sons
• Year: 1972
• Tongue: English
• Weight: 637 KB
• Volume: 4
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550040207

✦ Synopsis

The quantum yields of the sulfur dioxide triplet ( 3S02)-sensitized phosphorescence of biacetyl (+18en8) were deteryined in experiments with NZ-SO2-Ac2 and c-Cd-Il2-SOrAc2 mixtures excited at 2875 A at 27'C. The fraction of the biacetyl triplets which reacts homogeneously by radiative or nonradiative decay reactions was determined in a series of runs at constant [SO,]/[M] and [S02]/[Ac2] ratios but at varied total pressure. A kinetic treatment of the results and singlet sulfur dioxide ('SOZ) quenching rate constant data gave the following new kinetic estimates: ' SO2 + M + (SO2-M) (Ib); for 1S02-~-CBH12 collisions, k2b/(klb + k2b) = 0.073 f 0.024; previous studies have shown this ratio to be 0.095 f 0.005 for 'S02-SO2 collisions. It was concluded that the intersystem crossing ratio in 'SO2 induced by collision is relatively insensitive to the nature of the collision partner M. However, the individual rate constants for the collision-induced spin inversion of ' SO2 (k2b) and the total 'Sopquenching constants (klb + k2b) are quite sensitive to the nature of M: k2b/k2* varies from 0.10 f 0.03 for M = "L to 1.1 1 f 0.37 for M = c-Cd-i12, and ( k l b + k z b ) / ( k l a + varies from 0.29 for M = NZ to 1.44 for M = c-CgH12; kl, and k l b are the rate constants for the reactions 'SO2 + So2 + (2SO2) (la) and 'SOz + SO2 4 ?SO2 + SO2 (Za), respectively.

'so2 M + 3s02 f M (2b); for 's02-N~ collisions, kZb/(klb + k2b) = 0.033 f 0.008;