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ON THE LUMINESCENCE OF L ‐TRYPTOPHANE AND l ‐TYROSINE IN AQUEOUS SOLUTION AT 77dK INDUCED BY X‐RAYS AND U.V.‐LIGHT
Author(s) -
STEEN H. B.
Publication year - 1967
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1967.tb08894.x
Subject(s) - phosphorescence , luminescence , fluorescence , aqueous solution , excited state , photochemistry , chemistry , irradiation , singlet state , triplet state , ionization , analytical chemistry (journal) , molecule , atomic physics , materials science , ion , physics , optics , organic chemistry , optoelectronics , nuclear physics
— The lumincscence arising from L‐tryptophane and L‐tyrosine in aqueous solutions at 77d̀K during irradiation with u.v.‐light and with X‐rays has been studied. The spectra obtained with the two types of radiation were largely similar, differing only in that the yields of phosphorescence relative to fluorescence were considerably enhanced in the case of X‐irradiation. The decay times observed for the exponentially decaying phosphorescence, being 6.6 sec and 2.7 sec for tryptophane and tyrosine respectively, were the same for both kinds of irradiation. The G‐value of the X‐ray induced luminescence was about 10 for both tryptophane and tyrosine. Thus, about 30 per cent of the total energy absorbed from X‐rays in these compounds was re‐emitted as light. It was concluded that the X‐ray induced fluorescence and phosphorescence originate from the same levels as does the luminescence caused by u.v.‐light, i.e. the lowest excited singlet and the lowest triplet level of the aromatic structure of these compounds. In the case of X‐irradiation the enhanced ratios between the yields of phosphorescence and fluorescence indicated that some process other than excitation directly from the ground state contributed considerably to the luminescence yields. Assuming this process to be a recombination between the ionized molecule and its electron, it was calculated that the contribution to the luminescence yield from excitations directly from the ground state relative to that from ionizations, was negligible for both compounds.