Hydrated electron formation in nanosecond and picosecond laser flash photolysis of hematoporphyrin in aqueous solution.
Nanosecond (lambda exc = 266, 355 and 532 nm) and picosecond (lambda exc = 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 greater than 1000 mJ cm-2). The results show that e-aq are predominantly formed in a two-photon process at lambda exc = 266 and 355 nm. One-photon quantum yields are higher at lambda exc = 266 nm than at lambda 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 lambda exc = 532 nm. Nanosecond pulse-induced transient spectra obtained at pH 7.4 are also discussed.
Grabner
G
G
Institut für Theoretische Chemie und Strahlenchemie, Universität Wien, Vienna, Austria.
Getoff
N
N
Gantchev
T
T
Angelov
D
D
Shopova
M
M
D004583:Electrons; D006415:Hematoporphyrins / Q000737:chemistry*; D007700:Kinetics; D007834:Lasers; D008956:Models, Chemical; D008968:Molecular Conformation; D010782:Photolysis; D011827:Radiation; D012996:Solutions / Q000737:chemistry*; D013053:Spectrophotometry; D014867:Water / Q000737:chemistry
D006415:Hematoporphyrins; D012996:Solutions; D014867:Water