Neutron-proton interactions in heavy self-conjugate nuclei

• Main Author: Garnsworthy, Adam Benjamin
• Published: University of Surrey 2007
• Subjects: 539.754
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442671

Neutron-deficient nuclei along the proton drip line in the mass region 80-90 have been populated in relativistic projectile fragmentation reactions at GSI, Germany. A 750 MeV per nucleon beam of 107 47Ag60 provided by the SIS-18 synchrotron was fragmented on a 4 g/cm2 target of beryllium. The reaction products were separated and unambiguously identified using the Fragment Separator (FRS) with its ancillary detectors. The ions produced were slowed down by means of a variable thickness aluminium degrader and implanted in a 7 mm multilayer perspex block located at the centre of the high-efficiency Stopped RISING array. Gamma rays emitted from the decay of nano-to-millisecond isomeric states were detected in the array and correlated with the arrival of the associated ion. This allowed the observation of previously unreported excited states in the odd-odd N = Z nuclei, 82 41Nb41 86 43TC43. The new data suggest the low-lying structures of these proton drip line nuclei are dominated by a T = 1, np pairing condensate. Experimental results are compared to theoretical interpretations from TRS calculations and the Projected Shell Model. The isomeric state in 82Nb is interpreted as an isospin-changing K isomer with a reduced hindrance of fv ? 18. This is the first case of such an isomeric state along the N = Z line and indeed in this mass region. Previously unreported isomeric states have been identified in 87,88Tc and 84Nb. Isomeric ratios which provide insight into the reaction mechanism and nuclear structure are calculated for all the isomers observed, including the previously identified isomeric states in 94,96Pd, 93Ru and 84Nb.