https://doi.org/10.1007/s100530050173
Photofragmentation of hydrated iron ions Fe(H2O)n+ (n = 1-9) at 532, 355 and 266 nm
CEA, DSM/DRECAM/SPAM, Bâtiment 522,
CE Saclay,
91191 Gif-sur-Yvette Cedex, France
Corresponding author: a jmm@santamaria.saclay.cea.fr
Received:
11
November
1997
Revised:
18
February
1998
Accepted:
22
April
1998
Published online: 15 September 1998
Photofragmentation of Fe(H2O)
clusters (
) is investigated at three different wavelengths,
532, 355 and 266 nm. Two fragmentation pathways are
observed depending essentially on the photon energy, but also on the
parent size n. The fragmentation products belong to two
ion families, Fe(H2O)
and FeOH(H2O), which
correspond to dehydration and intracluster dehydrogenation
reactions respectively. The ion yields are studied
as a function of the laser fluence in order to determine the number
of photons implied in the photofragmentation process.
This allows us to estimate that the
D[ (H2O)
Fe+-(H2O)] bond energy is ranging between 0.44 eV
and 0.55 eV for 
.
Photon absorption cross sections are also derived
from the fluence experiments, and two different behaviors are
observed: i) At 355 nm, far away from any 
transition,
progressive solvation of the metal ion results
in an increasing absorption cross section from n=2 to n=9.
This can be attributed to
a forbidden transition of bare , which becomes progressively
allowed because of the
interaction with more and more water ligands.
ii) At 266 nm, close to
several allowed transitions of bare , a distinct maximum
is observed for the absorption of 
ion. It may be attributed
to a change in the spin multiplicity when switching from and
on one hand to Fe(H2O)
on the other.
PACS: 36.40.-c – Atomic and molecular clusters / 82.30.-b – Specific chemical reactions; reaction mechanisms
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1998
