Photoionization of Atoms

This chapter outlines the theory of atomic photoionization, and the dynamics of the photon-atom collision process. Those kinds of electron correlation that are most important in photoionization are emphasized, although many qualitative features can be understood within a central field model. The particle-hole type of electron correlations are discussed, as they are by far the most important for describing the single photoionization of atoms near ionization thresholds. Detailed reviews of atomic photoionization are presented in Refs. [I] and 121. Current activities and interests are well-described in two recent books [3,4

Book Review: \u3ci\u3eThe Theory of Atomic Structure and Spectra\u3c/i\u3e by Robert D. Cowan

The field of atomic spectroscopy is currently experiencing a resurgence of interest owing on the one hand to its applications in astrophysics, plasma physics, and other fields and on the other hand to the development of new experimental tools to probe atomic structures. One example of the latter is the use of tunable lasers to study highly excited atoms in the presence of strong external electric and magnetic fields. Another is the use of synchrotron radiation to probe with increasing detail the inner shell structure of rare earth, actinide, and other heavy atoms

Length and Velocity Formulas in Approximate Oscillator-Strength Calculations

The matrix element for electric dipole transitions is correctly given by the length formula in the Hartree-Fock, configuration-interaction, and related approximations, which involve the diagonalization of an approximate, but nonlocal, Hamiltonian

Book Review: \u3ci\u3eThe Theory of Atomic Structure and Spectra\u3c/i\u3e by Robert D. Cowan

The field of atomic spectroscopy is currently experiencing a resurgence of interest owing on the one hand to its applications in astrophysics, plasma physics, and other fields and on the other hand to the development of new experimental tools to probe atomic structures. One example of the latter is the use of tunable lasers to study highly excited atoms in the presence of strong external electric and magnetic fields. Another is the use of synchrotron radiation to probe with increasing detail the inner shell structure of rare earth, actinide, and other heavy atoms

Photoionization of Atoms

This chapter outlines the theory of atomic photoionization, and the dynamics of the photon-atom collision process. Those kinds of electron correlation that are most important in photoionization are emphasized, although many qualitative features can be understood within a central field model. The particle-hole type of electron correlations are discussed, as they are by far the most important for describing the single photoionization of atoms near ionization thresholds. Detailed reviews of atomic photoionization are presented in Refs. [I] and 121. Current activities and interests are well-described in two recent books [3,4

Discontinuities in the Electromagnetic Fields of Vortex Beams in the Complex Source/Sink Model

An analytical discontinuity is reported in what was thought to be the discontinuity-free exact nonparaxial vortex beam phasor obtained within the complex source/sink model. This discontinuity appears for all odd values of the orbital angular momentum mode. Such discontinuities in the phasor lead to nonphysical discontinuities in the real electromagnetic field components. We identify the source of the discontinuities, and provide graphical evidence of the discontinuous real electric fields for the first and third orbital angular momentum modes. A simple means of avoiding these discontinuities is presented.Comment: 10 pages, 4 figure

Angular distribution of electrons following two-photon ionization of the Ar atom and two-photon detachment of the F\u3csup\u3e-\u3c/sup\u3e ion

Angular-distribution asymmetry parameters for photoelectrons produced by two-photon ionization of the Ar atom and two-photon detachment of the F- ion are calculated for photon energies below the thresholds for single-photon ionization and single-photon detachment, respectively. Effects of electron correlations are included by perturbative methods. Good agreement is obtained between our results and those of a recent experimental angular-distribution measurement of two-photon detachment of the F- ion at λ=532 nm [C. Blondel, M. Crance, C. Delsart, and A. Giraud (unpublished)]

Random-phase approximation to one-body transition matrix elements for open-shell atoms

A graphical procedure is presented for evaluating each term in the equation satisfied by the first-order transition matrix for an arbitrary (open-shell) atom. For those terms involving the interaction of excited virtual pairs of electrons with the ionic core, we introduce the approximation that there is no exchange of orbital or spin angular momentum with the ionic core. This approximation is shown to lead to the random-phase approximation (RPA) equations in the closed-shell-atom case; we use it to define the RPA for open-shell atoms. The single equation satisfied by the first-order transition matrix is used to obtain a set of N+N′ coupled differential equations for N final-state radial functions and N initial-state radial functions, which together, completely determine the first-order transition matrix for an atomic system having N final-state channels. (The relation of N′ to N depends on the particular atom studied). The N+N′ differential equations are shown to reduce to familiar forms in the following cases: (1) When initial-state correlations are ignored, one obtains the close-coupling equations and (2) when closed-shell atoms are considered, N=N′ and one obtains the 2N coupled differential equations of the Chang-Fano version of the RPA. Finally, our RPA first-order transition matrix is used to evaluate the matrix element of the electric-dipole operator for an arbitrary (open-shell) atom. These RPA electric-dipole transition matrix elements may be used to calculate nonrelativistically all experimentally observable quantities resulting from a single-electron atomic photoabsorption process

Random-phase approximation to one-body transition matrix elements for open-shell atoms

A graphical procedure is presented for evaluating each term in the equation satisfied by the first-order transition matrix for an arbitrary (open-shell) atom. For those terms involving the interaction of excited virtual pairs of electrons with the ionic core, we introduce the approximation that there is no exchange of orbital or spin angular momentum with the ionic core. This approximation is shown to lead to the random-phase approximation (RPA) equations in the closed-shell-atom case; we use it to define the RPA for open-shell atoms. The single equation satisfied by the first-order transition matrix is used to obtain a set of N+N′ coupled differential equations for N final-state radial functions and N initial-state radial functions, which together, completely determine the first-order transition matrix for an atomic system having N final-state channels. (The relation of N′ to N depends on the particular atom studied). The N+N′ differential equations are shown to reduce to familiar forms in the following cases: (1) When initial-state correlations are ignored, one obtains the close-coupling equations and (2) when closed-shell atoms are considered, N=N′ and one obtains the 2N coupled differential equations of the Chang-Fano version of the RPA. Finally, our RPA first-order transition matrix is used to evaluate the matrix element of the electric-dipole operator for an arbitrary (open-shell) atom. These RPA electric-dipole transition matrix elements may be used to calculate nonrelativistically all experimentally observable quantities resulting from a single-electron atomic photoabsorption process

A Graphical Method for Calculating First Order Transition Matrices for Open-Shell Atoms in the Random Phase Approximation

A graphical procedure is presented for calculating first order transition matrices for a general (open-shell) atom. The first order transition matrix may be used to calculate matrix elements of a general one-body operator of rank λ in orbital space and σ in spin space. In the random phase approximation we obtain a set of N + N′ coupled differential equations for N final state radial functions and N′ initial state radial functions which completely determine the first order transition matrix for an atomic system having N final state channels. (The relation of N′ to N is dependent on the atomic system studied.) These N + N′ differential equations reduce to familiar forms in the following cases: (1) When initial state correlations are ignored, we obtain the N coupled differential equations of the Close-Coupling Approximation; (2) When the atom has only closed subshells we obtain N′ = N and the 2N coupled differential equations are those obtained in the Chang-Fano version of the Random Phase Approximation