<i>K</i> x-ray absorption spectra of chlorine in 3<i>d</i> transition-metal complexes

Abstract

The chlorine K absorption spectra from MnCl2⋅4H2O, FeCl2⋅nH2O, CoCl2⋅6H2O, NiCl2⋅6H2O, and CuCl2⋅2H2O have been investigated using a 50 cm bent-quartz crystal vacuum spectrograph. Chemical shifts are found for the first absorption maximum and discussed in relation to the d-electron affinities of the divalent metal ions. The first maxima are attributed to the transitions from the chlorine 1s level to the empty antibonding orbitals originating mainly from the metal 3d and chlorine 3p orbitals. The other absorption structures are alike through five different hydrated dichlorides and are ascribed to the core-level-to-empty-state transitions in the Cl− ion. The present spectra are compared with those of the anhydrous metal dichlorides MCl2 (M = Mn, Fe, Co, Ni, and Cu) reported previously. It is illustrated that the first peaks are varied little by changing the anhydrides into the hydrates, but the other structures are considerably altered.