Res. Chem. Intermed.
, Vol. 27, No. 7,8, pp. 891–900 (2001)
Potential traps for an excess electron in liquid water:
the trap lifetime distributions
W. M. BARTCZAK
and K. PERNAL
Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15,
93-590 Lodz, Poland
Department of Theoretical Chemistry, University of Lodz, Pomorska 149/153, 90-236 Lodz, Poland
Abstract—The possibilitiesof trapping of an excess electron by potential uctuations in liquid water
have been investigated by means of the computer simulation method.
The con gurations of water molecules generated by the Molecular Dynamics simulation were
searched for local minima of the potential energy. The analysis of a large set of the minima allows us
to obtain a statistical description of the microscopic trapping sites, including the distributions of the
trap energy, trapping power and volume. The estimated concentration of the electron traps in liquid
water is about 0.5 M.
The possiblity of electron trapping depends very strongly on the lifetime of the potential traps.
The simulations yielded the distribution of the trap lifetime with the average of 84 fs. A substantial
fraction (20%) of the traps live longer than 100 fs: a small fraction (0.2%) live as long as 1 ps. The
experimental measurementsof the electron hydration time give the results of the order of 100 fs. Thus,
the values of the trap lifetime obtained from our simulations support the ‘trap seeking’ mechanism of
the electron localization in water.
: Potential traps; potential uctuations; hydrated electron; water; computer simulation.
The injection of an excess electron into aqueous systems leads to a transient species
known as the hydrated electron, e
. Since its discovery in 1962 by Hart and
Boag  it has been a subject of continuous attention from both experimental and
theoretical researchers. After investigations by pulse radiolysis, starting from
range down to ps studies, the eld seemed to be well-recognized. The experimental
knowledge has been neatly summed up in numerous textbooks and monographs,
e.g.  to name a classic.
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Present address: Department of Chemistry, Florida State University, Tallahassee, USA.