https://doi.org/10.1007/s100530170080
Theoretical investigation of the ultrafast NeNePo spectroscopy of Au4 and Ag4 Clusters
Walther-Nernst-Institut für Physikalische und Theoretische Chemie, Humboldt-Universität Berlin, Bunsenstrasse 1,
D-10117 Berlin, Germany
Corresponding author: a vbk@chemie.hu-berlin.de
Received:
22
December
2000
Published online: 15 September 2001
Ultrafast ground state nuclear dynamics of Au4 and Ag4 is
theoretically explored in the framework of negative ion - to neutral - to
positive ion (NeNePo) pump-probe spectroscopy based on the ab initio Wigner
distribution approach. This involves the preparation of a nonequilibrium neutral
ensemble by pump induced photodetachment of a thermal anionic ground state
distribution, gradient corrected DFT classical trajectory
simulations "on the fly" on the neutral ground state, and detection of the
relaxation process of the ensemble in the cationic ground state by a
time-delayed probe pulse.
In Au4, the initially prepared linear structure is close to a local minimum
of the neutral state giving rise to characteristic vibrations in the signals
for probe wavelength near the initial Franck-Condon transition.
A timescale of ~1 ps for the structural relaxation towards
the stable rhombic D
neutral isomer was determined by the increase of
the signal for probe wavelength in vicinity of the vertical ionization
energy of the rhombic structure. In contrast,
the relaxation dynamics in Ag4 is characterized by normal mode vibrations
since both the initially prepared anionic ground state and the neutral ground
state have rhombic minimum geometries. Thus,
time-resolved oscillations of pump-probe signals are fingerprints of
structural behaviour which can be used experimentally for the
identification of particular isomers in the framework of NeNePo spectroscopy.
PACS: 31.15.Qg – Molecular dynamics and other numerical methods / 31.15.Ar – Ab initio calculations
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001
