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HYDRATED ELECTRON FORMATION IN NANOSECOND and PICOSECOND LASER FLASH PHOTOLYSIS OF HEMATOPORPHYRIN IN AQUEOUS SOLUTION
Author(s) -
Grabner G.,
Getoff N.,
Gantchev TS.,
Angelov D.,
Shopova M.
Publication year - 1991
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.1751-1097.1991.tb02074.x
Subject(s) - hematoporphyrin , flash photolysis , picosecond , nanosecond , photochemistry , aqueous solution , chemistry , photodissociation , flash (photography) , laser , optics , kinetics , organic chemistry , reaction rate constant , physics , photodynamic therapy , quantum mechanics
Nanosecond (λ cxc = 266, 355 and 532 nm) and picosecond (λ cxc . = 355 nm) laser flash photolysis of hematoporphyrin (Hp) was performed in neutral (pH 7.4) and alkaline (pH 12) aqueous solution, as well as in the presence of 0.1% Triton X‐100. The dependence of the yield of photoproduced hydrated electrons (e − aq ) on laser pulse energy was studied over a wide range of energies (0.2 to >1000 mJ cm −2 ). The results show that e˜, are predominantly formed in a two‐photon process at λ exc = 266 and 355 nm. One‐photon quantum yields are higher at λ exc = 266 nm than at λ exc = 355 nm. Both one‐photon and two‐photon pathways are less efficient at higher Hp concentration, reflecting the influence of Hp self‐aggregation. Two‐photon e aq formation is more efficient when 30 ps pulses are used for excitation, as compared to 10 ns pulses. No e − aq could be detected at λ exc = 532 nm. Nanosecond pulse‐induced transient spectra obtained at pH 7.4 are also discussed.