Calculation Of Photoionization Cross Sections Research Articles

Fits to new calculations of photoionization cross sections for low-Z elements

Analytical approximations to results of new calculations of partial (i.e. by subshell) photoionization cross sections of elements (2 < Z < 30, Z = 36) are presented which cover the photon energy range from near threshold to 300 keV. The computer program developed by Brysk and Zerby, which is based on the single-electron model and uses screened self-consistent field and Dirac-Slater wave function data furnished by Cromer, Waber and Liberman, was used. Sufficient multipoles were included to calculate the partial cross sections within a few per cent, on the assumed model. Results for several elements are compared with other calculations and measurements of total photoionization cross sections. The results are presented in a form most convenient for calculations of opacities of hot gases.

Calculation of photoionization cross sections of many-electron atoms

Calculation of photoionization cross sections of many-electron atoms

Effect of Core Polarizability on Photoionization Cross-Section Calculations

Demonstration of the importance of core polarizability in a case where cancellation is only moderate, with suggestion of an improvement to the scaled Thomas-Fermi (STF) wave functions of Stewart and Rotenberg (1965). The inclusion of dipole polarizability of the core for argon is shown to substantially improve the agreement between the theoretical and experimental photoionization cross sections for the ground-state configuration.

Spin-Orbit and Core-Polarization Effects in Potassium

The spin-orbit interaction and the correction to the dipole transition moment due to core polarization are included in a calculation of the potassium photoionization cross section. The computed spin orientation of photoejected electrons (Fano effect) and the behavior of the cross section in the region of its minimum are in harmony with recent measurements.

Photoionization Cross-Sections for Atoms and Ions of Sulfur

view Abstract Citations (92) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoionization Cross-Sections for Atoms and Ions of Sulfur Chapman, Robert D. ; Henry, Ronald J. W. Abstract We calculate photoionization cross-sections for all levels belonging to the configuration 1sI2sI2p63sI3p of atoms and ions of sulfur. Hartree-Fock functions are used to describe the bound atomic states which are required in the matrix elements for the cross-sections, and the close-coupling approximation is used to obtain continuum wave functions. The results are fitted to an interpolation formula which gives the cross-sections as a function of wavelength from threshold to 100 A. No extensive calculations have been made previously for these systems. Publication: The Astrophysical Journal Pub Date: August 1971 DOI: 10.1086/151072 Bibcode: 1971ApJ...168..169C full text sources ADS |

Photoionization cross sections of nitrogen, oxygen, carbon and argon for the Slater-Klein-Brueckner potential

An approximate central potential model was developed for the calculation of radial wave functions and photoionization cross sections. The model is based on combining the best features of the Slater approximation for the interior of the atom and the Klein-Brueckner approximation for intermediate and large electron radii. The outer subshell radial wave function for the N( 4 S) ground state term and the photoionization cross section for the N( 4 S)å N +( 3 P) transitions are compared with Hartree, Hartree-Fock-Slater, quantum defect approximate methods and with detailed Hartree-Fock solutions. Calculations of the photoionization cross sections for nitrogen, oxygen, carbon, and argon are presented for a range of electron energies from threshold to ≈ 30 eV. These data are compared with previous theoretical and experimental results. The present method brings the cross sections into close agreement with more detailed methods over the entire frequency range. However, the results do not always agree with experiment, and further improvements will require considerations of electron correlation effects.

Calculation of photoionization cross sections of Ba I

In order to explain the photoionization of artificial Ba clouds, it was necessary to calculate the corresponding cross sections from the ground state 6 s 2 1 S 0 and the metastable state 6 s5 d 1 D 2 of Ba I. They were calculated by use of the Many-Channel Quantum Method. No experimental cross sections are available, so direct comparison of the theoretical results is not possible. However, some quantities related to the 1 S → 1 P 0 cross section have been measured and the calculated values agree well. No similar data exist for the 1 D → 1 P 0 process. Moreover the calculations indicate that it will be difficult to measure directly this photoionization cross section due to the diffuse nature of the line in addition to the usual difficulties of populating the metastable initial state.

Correlation Effects in Atomic Structure Using the Random-Phase Approximation

Abstract : A procedure for treating correlations in atomic structure is introduced and applied to the calculation of excitation energies, oscillator strengths, and photo-ionization cross sections. The method is the extension of the Hartree-Fock theory known as the random-phase approximation, which has already been applied to a number of other many-body problems. In this application to atomic physics, results are given for the following atoms in column II of the periodic table: beryllium, magnesium, calcium, and strontium. These atoms all have 1 sub S ground states, and only excitations to 1 sub P states are considered. The general conclusion of the study is that the values of the oscillator strengths and photo-ionization cross sections are changed significantly by the correlations, while the changes in the values of the excitation energies are quite small. Wherever comparison with experiment is possible, the inclusion of these correlations improves the agreement between theory and experiment. Their effects are, however, not as marked as in highly degenerate infinite systems or in nuclei. (Author)

Photoionization from Outer Atomic Subshells. A Model Study

Calculations of photoionization cross sections are reported which emphasize the spectral range (from threshold to \ensuremath{\sim}150 eV above it) where the bulk of the optical oscillator strength is distributed and where the cross sections are large but experimental evidence is scarce. We have used as a model the light absorption by a single electron moving in a potential similar to the Hartree-Fock potential appropriate to the outer subshell of each atom. Data are reported for the rare gases He, Ne, Ar, and Kr, for Na, and for the closed-shell ions ${\mathrm{Cu}}^{+}$ and ${\mathrm{Ag}}^{+}$. Sum rules are used to analyze the oscillator strength spectral distribution and to attempt extrapolations to still higher energies. The results suggest a classification of atomic subshells into two types with fundamentally different spectral distributions of oscillator strength. One type consists of the subshells $1s$, $2p$, $3d$, $4f$, with nodeless radial wave functions, the other type includes all remaining subshells. The present calculations are regarded as a first approximation to be improved upon by taking into account configuration interaction.

A General Formula for the Calculation of Atomic Photo-ionization Cross Sections

A General Formula for the Calculation of Atomic Photo-ionization Cross Sections