Solution of Coupled Equations byR-Matrix Techniques

A realistic coupled-equation problem is solved using various $R$-matrix and level-matrix techniques. Comparison with exact coupled-equation calculations shows that excellent numerical results are possible with these methods, both in resonant and in nonresonant energy regions. The effects of varying the $R$-matrix boundary conditions and the number of levels included in the calculation are considered. Various aspects of $R$-matrix theory, such as the composition of $R$-matrix states, and the interference between neighboring levels, are illustrated by the calculations.