Isospin forbidden electroexcitation of the 1 −, T = 0 state at 6.95 MeV in 40Ca, continuum shell-model and effective charge of the convection current

Abstract

The isospin forbidden electroexcitation of the 1 −, T = 0 state at 6.95 MeV in 40Ca has been investigated for momentum transfers q = (0.18–0.51) fm −1. The longitudinal form factor exhibits a minimum at q = 0.19fm −1 indicating a destructive interference of the isoscalar and isovector parts. This behaviour is reproduced by a continuum shell-model calculation. A description of the transverse form factor leads to an effective proton charge of 0.5 for the δT = 0 convection current.