Channel-interaction effects on the3p-subshell photoionization of chlorine

Photoionization cross sections and photoelectron angular distributions (asymmetry parameters) are obtained for $3p$-subshell ionization of the Cl ground state. A substantial amount of bound-state electron correlation is taken into account through use of a multiconfiguration description of the ground state and residual ionic core. Both independent-channel and coupled-channel final states are used in evaluating the length and velocity forms of the dipole transition amplitudes. In the coupled-channel case, channel interaction is included via the reaction-matrix ($K$-matrix) method which diagonalizes the total $N$-electron atomic Hamiltonian in the manifold of single-channel basis states of the model Hamiltonian. In all of the ${}_{}{}^2{}_{}{}^{}D$ and ${}_{}{}^2{}_{}{}^{}P$ final-state channels, the photoabsorption transition probabilities exhibit significant contributions from interchannel interaction. In determining the cross sections for any of the ${}_{}{}^2{}_{}{}^{}S$ channels, it was necessary to include the low-lying $3s3p^6$; ${}_{}{}^2{}_{}{}^{}S$ bound state because of its large Coulomb interaction with the continuum of the $3p^4{}_{}{}^1{}_{}{}^{}D$, $\epsilon d$; ${}_{}{}^2{}_{}{}^{}S$ channel. The addition of the channels which originate from a $3s\to \epsilon p$ transition into the set of interacting ${}_{}{}^2{}_{}{}^{}S$ channels nearly cancels the effect of the $3s3p^6$; ${}_{}{}^2{}_{}{}^{}S$ discrete state on the cross sections of both the $3p^4{}_{}{}^1{}_{}{}^{}D$,$\epsilon d$; ${}_{}{}^2{}_{}{}^{}S$ and $3p^4{}_{}{}^1{}_{}{}^{}S$,$\epsilon s$; ${}_{}{}^2{}_{}{}^{}S$ channels. The asymmetry parameters for the three ionic multiplets ${}_{}{}^3{}_{}{}^{}P$, ${}_{}{}^1{}_{}{}^{}D$, and