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MO: Molekülphysik
MO 10: Spectroscopy I: Ultra-short Time Spectroscopy
MO 10.1: Vortrag
Donnerstag, 5. April 2001, 15:45–16:00, H1058
Generation of Solvated Electrons in Neat Water: Novel precursors from Femtosecond Spectroscopy — •A. Thaller, R. Laenen, T. Roth, and A. Laubereau — Technische Universitaet Muenchen, Physik-Department E11, James-Franck-Strasse, D-85748 Garching
We present data on the generation of solvated
electrons in neat water which extends to probing wavelengths of 5.5 µm
in
the mid IR. The electrons are generated via two photon absorption of the
third
harmonic (4.5 eV, 120 fs) of a regenerative amplified Ti:Sapphire laser.
From the data a strong shift of the maximum induced absorption is noticed
from
the MIR to the NIR which has almost finished after 200 fs. Secondly a
transient
isosbestic point is seen for the time intervall 75 fs to 150 fs around
1.85 µm. The first identified intermediate shows a
strong induced absorption centered at the peak absorption of the
OH-stretch,
but notably wider. For the next intermediate we find a
peak absorption at 1.6 µm with a weaker absorption extending to the
long
wavelength edge of our probing range.
The generation process is proposed to proceed due to a proton transfer
along
the H-bond of the excited water molecule resulting in an H3O+ and the
OH:e−-complex, the first intermediate identified from our data. The
excitation energy of 9 eV is too low for generation of electrons in the
conduction band of water. The absorption of the second novel precursor
is interpreted as a mix up of the absorption of hot ground-state electrons
within traps consisting of different numbers of water molecules.