  The results are presented on the study of the electronic structure of thorium
atoms adsorbed by the liquid atomic layer deposition from aqueous solution of
thorium nitrate on the surface of CaF2. The chemical state of the atoms and the
change of the band structure in the surface layers of Th/CaF2 system on CaF2
substrate were investigated by XPS and REELS techniques. It was found that
REELS spectra for Th/CaF2 system include peaks in the region of low energy
losses (3-7 eV) which are missing in the similar spectra for pure CaF2. It is
concluded that the presence of the observed features in the REELS spectra is
associated with the chemical state of thorium atoms and is caused by the
presence of uncompensated chemical bonds at the Th/CaF2 interface, and,
therefore, by the presence of unbound 6d- and 7s-electrons of thorium atoms.
Assuming the equivalence of the electronic configuration of thorium-229 and
thorium-232 atoms, an estimate was made on the time decay of the excited state
of thorium-229 nuclei through the channel of the electron conversion. It was
found that the relaxation time is about 40 {\mu}s for 6d-electrons, and about 1
{\mu}s for 7s-electrons.
