Spectroscopy around N=20 shell closure: β-n-γ decay studies of 33Mg and 35Al isotopes

Full text: The delayed neutron detector array TONNERRE was used, coupled with high efficiency γ-detectors, for a spectroscopic investigation of some neutron rich Mg and Al isotopes around the shell closure N = 20. The delayed neutron and γ spectra, following the β-decay of 33Mg and 35Al have been measured. A detailed analysis of such spectra allowed one to construct for the first time the level schemes of their daughters, 32,33Al and 34,35Si. The experiment was done at GANIL. The neutron rich 33Mg and 35Al have been produced using the projectile fragmentation of a high energy (78 MeV/nucleon) 36S beam. The ions of interest were selected by the double achromatic LISE3 spectrometer. At the end of LISE3, the beams were focused onto a detector telescope which provided for ion identification, collection and β-detection, located at the centre of the TONNERRE array. The TOF spectrum for delayed neutrons from 33Mg for the TONNERRE array and the TOF spectrum from low threshold neutron counters are shown. Also, we show the proposed decay scheme of 35Al nucleus. (author)