Measurement of x‐ray attenuation coefficients around K‐absorption edges using fe Kα x‐rays

Abstract

AbstractThe x‐ray mass attenuation coefficients were measured around the K‐absorption edges of elements in the range 16 ⩽ Z ⩽ 30 using Fe Kα x‐rays of energy 6.400 keV, which is the weighted average energy of Kα1 and Kα2 x‐ray components from the 57Co radioactive source. Kβ x‐rays were almost eliminated by the differential absorption technique. The small difference in energy between Kα1 and Kα2, 13 eV, was shown to be inconsequential by comparing the measured and theoretical values of μ/ρ for standard materials such as Al, Cu, Mo and Ta. The effect of fine structure of the K‐absorption edge on μ/ρ was elucidated by using the compounds of elements in the range 16 ⩽ Z ⩽ 30, containing one element with its K‐absorption edge energy (Ek) close to the incident photon energy (Ex). The results clearly indicate the validity of the theoretical mixture rule for all those compounds whose K edge is far away from the incident energy but show deviations of as much as 10% for the manganese compound whose K edge is 140 eV above Ex and about 12% for the chromium compound whose K edge is 410 eV below Ex. These deviations are attributed to the possible influence of resonance Raman scattering when the incident photon energy Ex is less than the edge energy and to the influence of EXAFS when Ex is more than the edge energy.