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Radiationless transitions between excited singlet states of biacetyl
Author(s) -
Richard C.,
Bouchy M.,
Andre J. C.,
Niclause M.
Publication year - 1978
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550100207
Subject(s) - excited state , chemistry , singlet fission , singlet state , quantum yield , atomic physics , phosphorescence , excitation , fluorescence , quenching (fluorescence) , photochemistry , inert gas , triplet state , physics , organic chemistry , quantum mechanics
Emission processes from lower excited states S 1 (fluorescence) and T 1 (phosphorescence) have been studied in the gas and liquid phases when biacetyl is excited into the second singlet state S 2 . (In agreement with Kasha's rule no fluorescence is observed from the S 2 state.) In the liquid phase, when biacetyl is excited into the singlet states S 1 and S 2 , no difference is observed between these emission processes. This phenomenon certainly results from an efficient nonradiative transition between the second excited singlet state S 2 and the first excited state S 1 with practically no excess vibrational energy. The quantum yield of this transition is almost unity and does not depend on the nature of the solvent. In the gas phase no emission processes are observed when biacetyl is excited into the S 2 state at low pressure (less than 10 mm Hg). High pressure of inert gas is necessary in order to observe these processes. As for excitation into the S 1 state with vibrational energy, loss of vibrational energy through collisions occurs from the S 2 state. The quantum yield of the S 2 → S 1 transition by excitation at 290 nm is estimated around 0.5–0.6 at 6 atm of inert gas (ethane, ethylene, or carbon dioxide).