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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. October 2002, Volume 1, Number 10, 503-526 |
Microscopic Solvation and Spontaneous Ionization of Li in Small
Polar Solvent Clusters: Theoretical Analysis of Photoelectron
Spectra for Li-(NH3)n
and Li-(H2O)n (n = 1-4)
Kenro Hashimoto, Kota Daigoku, Tetsuya Kamimoto, and Taku Shimosato
Internet Electron. J. Mol. Des. 2002, 1, 503-526
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Abstract:
The understanding of the electronic states of alkali atom embedded
in small polar solvent clusters is indispensable to construct a
microscopic model of solvation and dissolution of metals. In
connection to the recent photoelectron spectroscopy of negatively
charged Li-(NH3)n and
Li-(H2O)n, we have
carried out ab initio study for n
up to 4 to unveil the electronic change behind the n
dependence of their spectra. The cluster geometries were
investigated extensively by the second-order many-body
perturbation method with the 6-311++G(d,p) basis sets. The
vertical electron detachment energies for the transitions from the
anionic ground state to the neutral ground and low-lying excited
states were calculated by the multi reference single and double
excitation configuration interaction method. The most stable
structures of both Li-(NH3)n
and Li-(H2O)n for each n
tend to haveas many Li-nonhydrogen bonds as possible. The size dependence
of the vertical electron detachment energies for the 22S-,
22P- and
32S-type transitions at these geometries are in good agreement with
the experiment. The valence electrons of Li are squeezed out of the
solvation shell, giving rise to the spontaneous ionization of Li. The
solvated Li+ is surrounded by the diffused electrons in the n >= 3
anions. The spatial expansion of the unpaired electron distribution
also occurs in the neutral states with increasing n. The growing
one-center (Rydberg-like) ion-pair nature is responsible for the
rapid decrease of the energy separations between the ground and
the low-lying electronic levels of the neutrals, namely the red shifts
of the higher photoelectron bands.
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