J-matrix method: multichannel scattering and photoionization

The Jacobi- or J-matrix method introduced previously is extended to multichannel electron-atom scattering and photoionization in the LS-coupling scheme. The technique involves evaluation of only L 2 matrix elements and finite matrix operations, yet yields multichannel scattering information over a continuous range of energies. The approach in general, and the form of the formal solution for the reactance matrix in particular, bear close resemblance to R-matrix theory. The Wigner threshold laws for the cross sections and the Kato correction of the reactance matrix are discussed.