Collective effects in atomic photoabsorption spectra. III. Collective resonance in the 4d10shell in Xe

Abstract

For pt. II see abstr. A595 of 1972. The collective properties of the 4d¹⁰ shell in Xe are studied, making use of a previously developed method for analysing the linked diagram expansion for the polarizability. The infinite series of bubble and ladder diagrams (RPA with exchange) are considered for the (4d;nf)¹P channel and sum the on the energy shell part exactly. The off the energy shell part is given by a reaction matrix integral equation. An approximate, closed solution of Fredholm type is found to have two poles for energies between the continuum threshold and 2 Ryd above, in which region the exact reaction matrix equation cannot be solved by iteration. This result is interpreted in terms of a broad collective resonance in the (4d;nf)¹P channel, very clearly seen in the photoabsorption cross section. The theory is extended to include some effects of intershell interaction, representing core relaxation and improved agreement is found with experiments for low energies above the 4d⁹ threshold.