Thermal-vibration effect on X-ray integrated intensities near the copper K absorption edge in CuI: determination of the temperature factors

The energy dependence of the integrated intensities I_h(ω) and I_h(ω) and of their ratio r_h(ω), around an absorption edge, are greatly affected by thermal vibrations of atoms. This has been experimentally shown by the present energy-dispersive diffractometry for a mosaic crystal of CuI, for which thermal vibrations are especially large even at room temperature. The temperature factor values B_Cu = 3.3 ± 0.1 and B₁ = 2.0 ± 0.1 Ų have been determined in the following way: the f”_Cu(ω) curve has been determined from the absorption curve, and therefrom the f'_Cu(ω) curve has been calculated by the dispersion relation. By the use of these curves, the intensity curves I₅₅₅(_ω) and I(ω) were obtained, and then the temperature factors were determined by finding the best fit between the above I(ω) curves and the observed one. Also, the experimental fine structure of the Friedel ratio r₅(ω) is shown as a function of energy and compared with the calculated values.