A gamma ray study of 40K

The electromagnetic decay scheme of 40K below an excitation of 3.2 MeV has been measured using the 37Cl( alpha ,n)40K reaction in conjunction with both a Si(Li)-Ge(Li) and a Ge(Li)-NaI(Tl) coincidence system. Gamma ray angular distribution and angular correlation measurements were also made using both the 40Ar(p,n)40K and 37Cl( alpha ,n)40K reactions. Four unique spin assignments were made to levels at 2398 keV (4-), 2419 keV (2-), 2787 keV (3) and 3147 keV (1). Spin restrictions were placed on other levels, and both branching ratios and multipole mixing ratios determined for several transitions. A shell model calculation using the effective surface delta interaction was performed. The predictions, in good agreement with the present experimental results, showed that the low lying states of positive parity are well described by two particle two hole excitations involving only the 1d3/2 and 1f7/2 orbits.