Electromagnetic transition rates in 38Cl and 40K

The attenuated-Doppler-shift method was used to measure the mean lives of low-lying states in ³⁸Cl and ⁴⁰K. States were populated by the (d, p) reaction and the recoil direction was defined by coincidence with the outgoing proton. While the positions of the levels in these two nuclei give encouragement to the belief that many of the states are well described as members of simple particle-hole or particle-particle multiplets, it is immediately apparent that the magnetic dipole transition rates do not fit the simple picture even if effective moments are used. A recent theoretical study has shown that some admixtures that can be expected will significantly alter the M1 rates, but the present results are not in good agreement with the theoretical predictions. Other available lifetime data on these nuclei support the present contention that there are severe discrepancies between the observed rates and those predicted by the best available shell-model calculations.