The experimental As K-edge x-ray-absorption fine structure of ${\mathrm{As}}_2$${\mathrm{S}}_3$ is analyzed in detail and compared to data calculated theoretically from a model structure. The experimental spectrum is resolved into two components, one representing a bound excited state resonance and a second due to transitions to the continuum. The bound state resonance is located 6.1 eV below the continuum threshold and is fitted by a Lorentzian. The continuum structure is constructed using theoretically calculated χ and absorption cross section data together with an arctangent function simulating the absorption and lifetime at the continuum edge. For the theoretical calculation, the ab initio code feff was applied to an atomic cluster representing the amorphous solid. The results show that multiple scattering effects give rise only to small contributions in the region of the continuum threshold. They are negligible for higher energies.

• Received 31 May 1994

DOI:https://doi.org/10.1103/PhysRevB.51.804