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ETUDE PAR RESONANCE PARAMAGNETIQUE ELECTRONIQUE ET PAR SPECTROPHOTOMETRIE D'ABSORPTION DES PROCESSUS PRIMAIRES DANS LA PHOTOCHIMIE DE SOLUTIONS AQUEUSES CONGELEES A 77°K D'ACIDES AMINES AROMATIQUES ET DE POLYPEPTIDES *
Author(s) -
SANTUS R.,
HÉLÈNE C.,
PTAK M.
Publication year - 1968
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.1751-1097.1968.tb08023.x
Subject(s) - chemistry , aqueous solution , photochemistry , absorption (acoustics) , solvent , radiolysis , irradiation , absorption spectroscopy , absorption band , solvated electron , resonance (particle physics) , electron paramagnetic resonance , hydrogen , atomic physics , nuclear magnetic resonance , physics , organic chemistry , quantum mechanics , acoustics , nuclear physics , optics
— Neutral, acidic or basic frozen aqueous solutions of aromatic amino acids undergo photoionisation under u.v. irradiation, at 77°K. In neutral or basic solutions, photo‐ejected electrons are trapped in the solvent matrix and exhibit a characteristic absorption band in the visible region. In acidic solutions electrons are trapped by protons and ESR signal spectrum of hydrogen atoms may be observed. Hydrogen atoms are also produced in low yield in neutral or basic frozen aqueous solutions, u.v. irradiated at 77°K. In basic media the ESR spectrum of 0 ‐ radical ions is observed. Kinetic studies as a function of light intensity show that photoionisation takes place after absorption of a second photon by the phosphorescent molecule in its lowest triplet state. Recombination of trapped electrons in neutral or basic solutions may be induced using secondary excitation with visible light. In all instances we could record the absorption spectrum of photolytic products of aromatic amino acids and polypeptides which are u.v. irradiated at 77°K.