Backward-angle high-resolution inelastic electron scattering on 40, 42, 44, 48Ca and observation of a very strong magnetic dipole ground-state transition in 48Ca

Abstract The search for magnetic dipole transitions from the ground state-even Ca isotopes to high lying J π =1 + states by means of low momentum transfer but high resolution inelastic electron scattering is described. The previously detected strongly excited J π =1 + state E X =10.319 MeV [ B (M1)↑=1.12±0.27 μ K 2 ] in 40 Ca has been confirmed, but - contrary to the expectations of the independent particle shell model - only a fairly weak M1 transition is observed in 42 Ca [E X = 11.235 MeV , B( M 1)↑=0.59±0.05 μ 2 K ] and none in 44 Ca between E X=8.2−12.2 MeV . In 48 Ca, however, a very strong M1 transition [ B (M1) ↑ = 4.0 ± 0.3 μ 2 K ] to a single state at E X =10.227 MeV has been discovered.