Spin-orbit effects in aluminum photoionization

Abstract

The eigenchannel R-matrix approach, in conjunction with the multichannel quantum-defect theory and the LS~j j recoupling frame transformation, is used to calculate the photoionization spectrum of Al i below the 3s3p P ionization threshold (photon energies in the range 0.44 ( tub ( 0.98 Ry). Relativistic channel mixing is incorporated in the calculations by a recoupling frame transformation and by the inclusion of experimental 6ne-structure threshold energies. This mixing enables autoionization of resonances whose decay would otherwise be forbidden in the pure LS-coupling scheme. The calculated J-dependent energies and widths agree well with those of experimental resonances. The complicated relativistic spectrum, with up to 11 interacting channels, provides an experimentally realizable testing ground for studies of statistical properties of resonances. The spectrum below the 3s3p P ionization threshold exhibits the Wigner and Porter-Thomas distributions of positions and widths of resonances, respectively. While portions of the aluminum spectrum appear to be random, according to these measures, there remains much underlying regularity in the level spacing and width distributions.PACS number(s): 32.80. Fb, 31.15.+w, 32.30.r, 05.45.+b

R-matrix Calculation of C III Bound and Continuum Fine-structure States

“…causing a shift in the resonance structures con-1s22p 1@2, 3@2 ), verging there. These e †ects are well illustrated in a recent calculation on Al [17], using an eigenchannel R-matrix approach for photoionization with spinÈorbit e †ects and a core polarization model potential.…”

Use of partial-wave decomposition to identify resonant interference effects in the photoionization–excitation of argon

“…Photoionization cross sections for Ar have also been obtained theoretically using the ab-initio R-matrix approach [19], which was extended to use multi-configuration Hartree-Fock (MCHF) orbitals for the description of residual states of Ar II [20]. A detailed description of how photoionization cross sections are determined in LS-coupling has been given previously [21,22].…”

Theoretical photoionization spectra in the UV photon energy range for a Mg-like Al+ion

“…Theoretical and experimental studies for photoabsorption of the Al + ion have been performed by several authors [5][6][7][8][9][10][11]. Recent measurements of absolute cross sections for Al + ion were performed by West et al [2], where they reported strong peaks in the photoionization cross section for the Al + ion from 20 to 26 eV as being due to the significant influence of fourth-order radiation.…”