Effective shell-model transition operators for muon-capture calculations

Recently many shell-model calculations have been performed in order to extr act the value of the ratio C-P/C-A in light nuclei. Most of these calculati ons fail to reproduce the value given by the partially conserved axial vect or hypothesis, roughly 7. We show that, with the effective transition opera tors calculated by the perturbative techniques, this discrepancy can be, at least partly, solved. New angular correlation data for Si-28 are used for the extraction of C-P/C-A In the case of Ne-20, the capture rate data are u sed for the extraction. (C) 2000 MAIK "Nauka/Interperiodica".