Beta-decay of "2"0Mg

The #beta#-decay of "2"0Mg was investigated. A secondary beam of "2"0Mg ions, produced in reactions between a 95 A x MeV "2"4Mg-beam and a "n"a"t".Ni-target, was isotopically separated by means of the LISE3 spectrometer at GANIL. This secondary beam was implanted into a silicon detector array surrounded by germanium #gamma#-detectors. The #beta#-delayed proton and #gamma#-ray data, measured for this short-lived nucleus (T_1_/_2=95#+-#3 ms), were incorporated into an improved "2"0Mg#->#"2"0Na decay scheme. The 2645 keV level in "2"0Na is of importance for the breakout from the astrophysical hot CNO-cycle and the onset of the rapid proton capture process via the reaction "1"9Ne(p,#gamma#)"2"0Na. An upper limit of 0.1% for the #beta#-decay feeding of the 2645 keV level and a lower limit for the corresponding log ft value of 6.24 were determined. The implications of this result for the spin and parity assignment of the 2645 keV state are discussed. Concerning the isobaric multiplet mass equation no significant deviation from its quadratic form was found. By comparing the "2"0Mg #beta#-decay into the proton-unbound 3001 keV state in "2"0Na and the isospin-mirrored decay into the particle-bound 3488 keV level in "2"0F, an asymmetry ft"+/ft"--1=1.69_-_0_._6_5"+"0"."8"6 was observed. (orig.)SIGLEAvailable from TIB Hannover: RO 801(94-52) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman