Conversion between the Formal and Observed Parameters in R-matrix Theory

Abstract

The conversion between the formal and observed parameters is obtained from the phase equivalence between the R-matrix and Breit-Wigner formula, and it is applied to a study of the low-energy E1 Sfactor of 12 C(α,γ 0 ) 16 O. As an example, weak interference between 1 − states in 16 O is discussed. As well as the ordinary R-matrix method, the present method calculates the S -matrix and cross sections, independent of the boundary condition. Therefore, the E1 S -factor at E c.m. = 300 keV is found to be reduced from the current evaluation.