Intersystem crossing and internal conversion in benzene vapour at low pressures
- 1 January 1976
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
- Vol. 72, 2044-2054
- https://doi.org/10.1039/f29767202044
Abstract
The pressure dependence of triplet formation in C6H6 and C6D6 excited at 253.7 nm was studied using both but-2-ene sensitized isomerization and biacetyl phosphorescence. Pressures were varied between 0.1 and 20 Torr by addition of argon. The triplet yield decreases as the pressure decreases from 0.70 at high pressures ( 8 Torr) to 0.18 at 0.1 Torr in C6H6 and from 0.65 to 0.11 in C6D6. The results are interpreted in terms of a collisional assisted intersystem crossing S1 [graphic omitted] → T2 in the low pressure region. For pressures above 1 Torr the observed pressure dependence is attributed to a reversible intersystem crossing process S1 [graphic omitted] → T2. It is shown that a decrease in triplet lifetime with an increase in vibrational energy does not explain the present observations even at the lowest pressures used. The results show also that internal conversion S1 [graphic omitted] → S0 is an important channel of nonradiative decay in the lowest excited singlet state of C6H6 and C6D6.Keywords
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