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Picosecond study of aqueous tryptophan and indole photoionization
132 Picosecond study of aqueous tryptopban and indde photoionization
J. C. MIALOCQ Dipartement
de Physicochimie,
Centre d’Etudes
Nuc&zires
de Saclay,
9119i
Gif SW Yvette Ct+dex
(Frunce) E. AMOLJYAL, Universit2
A. BERNAS
Paris-Sud,
91405
and
Orsay
D. GRAND
Ckdex (France)
In a double-beam picosecond spectrometer single pulses of about 20 ps duration at 265 nm were used to investigate the photoionization of aqueous solutions of tryptophan (Trp) and indole (Ind). Hydrated-electron (e,-) absorption was monitored at 660 nm, and in the presence of Cd’* as an electron scavenger the absorptions of the indole radical cation IndH+ (at 600 nm) and of the neutral radical Ind* (at 530 nm) were recorded. For both solutes, the e,,absorption appears within the time of the laser pulse and electron ejection and solvation occur in a time which is several orders of magnitude shorter than the lifetime of the fluorescent state. Under the present experimental conditions the e aq formation results from equal contributions of a one-photon and a sequential two-photon mechanism. Thus in the monophotonic ionization, e,, very probably originates from the unrelaxed first excited singlet state and not from the fluorescent state. The e, optical density remains constant from 100 ps to 1.7 ns, which implies that no appreciable charge recombination occurs during that time.
Picosecond study of radiationless relaxation processes in biliverdin dimethyl ester
A.R.
HOLZWARTH
Institut D-4330
fir
Strahlenciaemie im Max-Planck-Institut Miilheim a. d. Ruhr (F. R. G.)
T. GILLBRO Division
and
of Physical
fir Kuklenforschung,
Stiftwrasse
34 - 36,
V. SUNDSTROM Chemistry,
University
of Ume&, S-90187
Ume&
(Sweden)
Picosecond decay kinetics of both unprotonated (BVE) and protonated (BVEH+) biliverdin dimethyl ester were studied as a function of temperature in C2H50H and methyl tetrahydrofuran (MTHF). The source of picosecond pulses was a synchronously mode-locked and cavity-pumped dye laser system. The experimental arrangement has been described elsewhere [l]. Except for BVE in neutral MTHF, double-exponential decays were observed under all conditions. This is in agreement with previous studies on the conformational inhomogeneity
J. C. MIALOCQ Dipartement
de Physicochimie,
Centre d’Etudes
Nuc&zires
de Saclay,
9119i
Gif SW Yvette Ct+dex
(Frunce) E. AMOLJYAL, Universit2
A. BERNAS
Paris-Sud,
91405
and
Orsay
D. GRAND
Ckdex (France)
In a double-beam picosecond spectrometer single pulses of about 20 ps duration at 265 nm were used to investigate the photoionization of aqueous solutions of tryptophan (Trp) and indole (Ind). Hydrated-electron (e,-) absorption was monitored at 660 nm, and in the presence of Cd’* as an electron scavenger the absorptions of the indole radical cation IndH+ (at 600 nm) and of the neutral radical Ind* (at 530 nm) were recorded. For both solutes, the e,,absorption appears within the time of the laser pulse and electron ejection and solvation occur in a time which is several orders of magnitude shorter than the lifetime of the fluorescent state. Under the present experimental conditions the e aq formation results from equal contributions of a one-photon and a sequential two-photon mechanism. Thus in the monophotonic ionization, e,, very probably originates from the unrelaxed first excited singlet state and not from the fluorescent state. The e, optical density remains constant from 100 ps to 1.7 ns, which implies that no appreciable charge recombination occurs during that time.
Picosecond study of radiationless relaxation processes in biliverdin dimethyl ester
A.R.
HOLZWARTH
Institut D-4330
fir
Strahlenciaemie im Max-Planck-Institut Miilheim a. d. Ruhr (F. R. G.)
T. GILLBRO Division
and
of Physical
fir Kuklenforschung,
Stiftwrasse
34 - 36,
V. SUNDSTROM Chemistry,
University
of Ume&, S-90187
Ume&
(Sweden)
Picosecond decay kinetics of both unprotonated (BVE) and protonated (BVEH+) biliverdin dimethyl ester were studied as a function of temperature in C2H50H and methyl tetrahydrofuran (MTHF). The source of picosecond pulses was a synchronously mode-locked and cavity-pumped dye laser system. The experimental arrangement has been described elsewhere [l]. Except for BVE in neutral MTHF, double-exponential decays were observed under all conditions. This is in agreement with previous studies on the conformational inhomogeneity