E. Hudson et al., NEAR-EDGE SODIUM AND FLUORINE K-SHELL PHOTOABSORPTION OF ALKALI-HALIDES, Physical review. B, Condensed matter, 49(6), 1994, pp. 3701-3708
The x-ray-absorption near-edge structure (XANES) spectra of single-cry
stal alkali halide salts have been measured at low temperature (T almo
st-equal-to 80 K) with high resolution in energy. By employing the ele
ctron partial-yield detection technique, spectra of NaF, NaCl, and NaB
r were obtained near the sodium K edge and spectra of LiF, NaF, and KF
were obtained near the fluorine K edge. All spectra showed sharp abso
rption features at the absorption threshold and broader features exten
ding 50-80 eV above threshold. Some narrow features close to threshold
are attributed to core-level excitons. Contributions from atomic mult
iple-electron excitations, estimated by a comparison to the K-edge pho
toabsorption spectrum of Ne in the gas phase, are found to be very sma
ll. Thus, the intense broader peaks observed further above threshold a
rise from single-electron scattering resonances. These highly structur
ed spectra of well-characterized ordered crystals provide a set of sta
ndard data which is used to test the multiple-scattering x-ray-absorpt
ion code FEFF V. For some spectra, at photon energies more than almost
-equal-to 10 eV above threshold, the calculations achieve very good ag
reement with experiment. The dependence of the calculation on cluster
size, order of scattering, and choice of self-energy is demonstrated.