Chemical shifts of the LIII absorption discontinuity of rhenium

Chemical shifts of the X-ray L_III absorption discontinuities of rhenium in some of its binary and ternary compounds have been studied using a bent crystal X-ray spectrograph. The chemical shifts (ΔE) are found to be governed by the effective charges (q) on the absorbing ions, which have been calculated using Suchet's theory. For the compound ReCl₅, however, the effective ionic charge cannot be calculated since the pentavalent radius of rhenium is not known. The ΔE, q plot has been used to determine the charges on the rhenium ions in ReCl₅ as well as in two ternary compounds KReO₄ and NaReO₄. Our work has enabled us to determine the ionic radius of pentavalent rhenium.