Polarized experimental and theoretical K-edge x-ray absorption studies of ${\mathrm{SO}}_4^{2\mathrm{-}}$, ${\mathrm{ClO}}_3^{\mathrm{-}}$, ${\mathrm{S}}_2$${\mathrm{O}}_3^{2\mathrm{-}}$, and ${\mathrm{S}}_2$${\mathrm{O}}_6^{2\mathrm{-}}$

The first studies of the polarized sulfur and chlorine x-ray K-edge absorption spectra of the oxyanions ${\mathrm{SO}}_4^{2\mathrm{-}}$ (sulfate), ${\mathrm{ClO}}_3^{\mathrm{-}}$ (chlorate), ${\mathrm{S}}_2$ ${\mathrm{O}}_3^{2\mathrm{-}}$ (thiosulfate), and ${\mathrm{S}}_2$ ${\mathrm{O}}_6^{2\mathrm{-}}$ (dithionate) are presented. To provide a basis for the interpretation of the experimental measurements, extended continuum multiple-scattering Xα computations were carried out. This approach enabled us to identify features in the absorption spectra both by symmetry and final-state type (final bound states or final continuum states). For the thiosulfate anion (which has two nonequivalent sulfur atoms) it proved possible to determine which sulfur atom is responsible for each of a series of well-resolved features in the polarized spectra. In addition, generalizing from the case of the chlorate anion, molecules in which the absorbing atom is not completely surrounded by ligands (‘‘open clusters’’) may have important contributions from the second shell of neighbors manifested as features in the continuum region of the spectrum.