Spectroscopy Near the N=20 Shell Closure: $\beta$-n Decay Studies of $^{33}$Mg and $^{35}$Al

Abstract : An experimental spectroscopic investigation of some neutron rich Mg and Al isotopes around the shell closure N=20 has been performed. The delayed neutron and $\gamma$ spectra, following the $\beta$-decay of $^{33}$Mg and $^{35}$Al have been measured using the delayed neutron detector array TONNERRE coupled with high efficiency EXOGAM clover detectors, a LEPS detector and eight low-energy neutron detectors. A detailed analysis of such spectra allows one to construct the level schemes of their daughters, $^{32,33)$Al and $^{34,35}$Si. The resulting spectroscopic information will provide stringent tests of large scale shell model calculations including np - nh excitations aimed at the understanding of the structural effects occurring in this region.