l-Forbidden M1 Transition in ³²S: A Test of Tensor Corrections to the Magnetic Dipole Operator

The extremely weak l-forbidden 1d_3/2→2s_1/2 magnetic dipole ( M1) transition from the ground state of ³²S to a J^π  =  1⁺ state at E_x  =  7.003  MeV was investigated by 165° and 180° electron scattering. The extracted strength of 0.0040(5)μ_N² represents the smallest B(M1)↑ value ever measured in electron scattering. A combined analysis with the isospin-analogous Gamow-Teller (GT) decays of the J^π  =  1⁺ ground states of ³²Cl and ³²P is performed. Empirical corrections of Brown and Wildenthal to the magnetic operators reasonably account for the data. Corrections derived from microscopic approaches are less successful pointing towards a fundamental, not yet understood problem in the description of the effective M1 and GT operators.