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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 6, Number 4
April 20, 1985 

Nanosecond Laser Flash Photolysis Study of 5-Styryl-1,3-dimethyluracil
Sang Chul Shim, Eun Ju Shin, Kyu Ho Chae
The photoisomerization of 5-styryl-1,3-dimethyluracil is studied with nanosecond laser flash photolysis technique at room temperature. The laser flash photolysis of E-isomer produces the transient absorption spectrum regarded as the triplet-triplet absorption, but the transient absorption of Z-isomer does not show the typical decay curve, probably due to the facile photocyclization reaction during the laser flash photolysis. Using the energy transfer method on nanosecond laser spectroscopy, the energy of the lowest triplet state for E isomer is estimated to lie between 41.8 and 47 kcal/mol. The triplet lifetime for E-isomer obtained from the decay curve of the transient absorption is ca. 93ns. The S1 → T 1 intersystem crossing of E-isomer on direct excitation is relatively inefficient at room temperature supporting the singlet mechanism for direct photoisomerization.
234 - 238
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