Subshell photoionization

D.A. Vemer, D.G. Yakolev, I.M. Band, M.B. Trzhaskovskaya, Subshell photoionization cross sections and ionization energies of atoms and ions from He to Zn, At. Data Nucl. Data Tabl. 55 (1993)233. 

Schofield, J. H. (1976). Hartree-Fock subshell photoionization cross-sections at 1254 and 1487 eV. J. Electron Spectrosc. Relat. Phenom. 8, 129-37. 

Table 6.6 Theoretical atomic subshell photoionization cross-sections for MoVTeNb-related valence band orbitals at different photon energies, according to the calculations ofYeh and Lindau [177].

The theoretical calculation for peak intensity of photoelectron spectram has been carried out in the framework of DV-Xa method. First we ealculate the atomic subshell photoionization cross sections. The photoionization cross section for atomic orbital... 

Fig. 6. Ba 4d"Hkf subshell photoionization cross sections calculated by Wendin, ref. 58. Expt. by Rabe et al., ref. 58a, normalized to contain 10 electrons.

A compilation of subshell photoionization cross sections for the six elements at Al Ka radiation energy (1486.6 eV) scaled to of Na (0.118Mb), derived from photoelectron spectrometry, can be found in [11]. See also [12, 13]. 

The latter equation assumes a 100% linearly polarized ionizing radiation, a is the fine structure constant, Nni is the number of electrons in a nl subshell, Dni->ei l is a radial dipole photoionization amplitude, fini is the dipole photoelectron angular asymmetry parameter, and A i2 is the electric dipole-quadrupole interference term arising due to the correction term ikr in the above expression for Mab,... 

In the framework of the A-potential model, combined with the frozen-cage approximation, the problem is solved simply. Namely, HF wavefunctions and energies of the encaged atom, solutions of the extended to encaged atoms Hartree-Fock equations (2), must be substituted into corresponding formulae for the photoionization of an nl subshell of the free atom, Equations (18)-(26), thereby turning them into formulae for the encaged atom (to be marked with superscript " A") rrni(o>) —> a A(co), Pni(fi>) Yni o>) - and 8ni((o) - 8 A(co). This accounts... 

The dependence of confinement resonances on quantum numbers of the ionized subshell nl can be illustrated by the 5-potential model calculated data [34] for the Ne Is and 2s photoionization cross sections from Ne C60, see Figure 5. 

The discovery of confinement resonances in the photoelectron angular distribution parameters from encaged atoms may shed light [36] on the origin of anomalously high values of the nondipole asymmetry parameters observed in diatomic molecules [62]. Following [36], consider photoionization of an inner subshell of the atom A in a diatomic molecule AB in the gas phase, i.e., with random orientation of the molecular axis relative to the polarization vector of the radiation. The atom B remains neutral in this process and is arbitrarily located on the sphere with its center at the nucleus of the atom A with radius equal to the interatomic distance in this molecule. To the lowest order, the effect of the atom B on the photoionization parameters can be approximated by the introduction of a spherically symmetric potential that represents the atom B smeared over... 

For outer subshells of the encaged atom, the ionization thresholds of which vary from a few eV to a few tens eV, the dynamical-cage model is required. The photoionization cross section of the encaged atom in the dynamical-cage approximation will be marked with a tilde sign 5 s and... 

Figure 18 Calculated [33] RPAE results for the Xe 5s photoionization cross section of Xe Cgo obtained in the A-potential model at the frozen-cage approximation level. (a) o 1" A iro), complete RPAE calculation accounting for interchannel coupling between photoionization transitions from the Xe 4d10, 5s2 and 5p6 subshells (b) 5 A ( >), the same as in (a) but with the 4d - f, p transitions being replaced by those of free Xe, for comparison purposes (c) o AA(

Relativistic effects in photoionization of atoms encaged in C60/ A Cso, have fallen under theoretical scrutiny in [29,30], where the photoionization spectra of valence ns subshells in encaged alkaline-earth-metal atoms ( Mg, Ca, Sr and Ba) were detailed. The corresponding key results of [29,30] are highlighted in this section. 

The a s are the relative photoionization cross-sections of a parti( ular atomic subshell they have been obtained by a fitting procedure on reference systems. 

The calculations of the photoionization cross section of the atomic subshell have previously been performed using Hartree-Fock-Slater one-electron model by several workers. Table 1 compares the photoionization cross sections of the atomic orbital electrons obtained in the present work with those previously reported by Scofield for some atoms. Scofield has used the relativistic wave functions. The... 

The value of the photoionization cross section varies for a different photon energy. Figure 2 plots the photoionization cross sections of the atomic orbitals for Fe atom as a function of the photon energy. Yeh and Lindau have reported the photoionization cross sections of atomic subshells for various photon energies. The present result is in a good agreement with the previous calculations. 

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