Alternative parametrization of<i>R</i>-matrix theory

Abstract

An alternative parametrization of $\mathit{R}$-matrix theory is presented which is mathematically equivalent to the standard approach, but possesses features that simplify the fitting of experimental data. In particular, there are no level shifts and no boundary-condition constants which allow the positions and partial widths of an arbitrary number of levels to be easily fixed in an analysis. These alternative parameters can be converted to standard $\mathit{R}$-matrix parameters by a straightforward matrix diagonalization procedure. In addition, it is possible to express the collision matrix directly in terms of the alternative parameters.