  The new results are presented of the experimental study of KNbO3 and KTaO3 by
means of X-ray photoelectron spectroscopy, soft X-ray emission and X-ray
fluorescence spectroscopy. In particular, Nb M(4,5) spectra have been measured
over a range of near-threshold excitation energies 206.5 - 240.6 eV, and Ta
N(3) spectra over 399.4 - 420.4 eV at the Advance Light Source in Berkeley.
These spectra were found to be strongly dependent on the excitation energy.
Moreover, the O K(alpha) X-ray emission spectra in both compounds as well as
the valence-band photoelectron spectra are brought to the binding energy scale
and discussed in combination. The trends in the spectra are explained on the
basis of first-principles band-structure calculations, with the dipole
transition matrix elements taken into account.
