Experimental and theoretical studies of extended x-ray absorption fine structure in bromine salts (NaBr and KBr)

The x-ray absorption fine structure above the $K$ edge of the bromine ion in KBr and NaBr has been measured on powdered samples using synchrotron radiation from the Stanford's storage ring SPEAR, at liquid-nitrogen temperature and room temperature. Comparison of the results is done with simple calculations where a model for the crystal potential is built starting from atomic potentials, and the phase shifts are computed with a Slater approximation for the exchange term; the limitations of the present theories are due to the fact that the agreement is only semiquantitative, even if it must be kept in mind that ionic solids are not the best samples, and that the calculations are not very sophisticated.