Nuclear structure of proton-rich intermediate mass nuclei studied with advanced lifetime measurement techniques

The transition matrix elements between excited nuclear states provide valuable information about the structure of exotic nuclei. Lifetime measurements are a model-independent way to deduce these matrix elements from experimental data. Two studies of proton-rich nuclei near mass 70 are presented herein using advanced lifetime measurement techniques.;The first study is a measurement of the 81+ and 91+ states in the odd-N, odd-Z nucleus 70As. The lifetimes of these states were determined by the application of the gamma-ray lineshape method to gamma-gamma coincidence data. The states were populated using with the 9Be(78Rb,70As) reaction and gamma rays were detected with the Segmented Germanium Array in coincidence with reaction products detected in the focal plane of the S800 Spectrograph. The B(E1;8+ →7 -) and B(M1;9+→8 +) transition strengths were deduced and were found to support the assignment of these states to a coupling of the odd proton and neutron in the g9/2 orbital.;The second study is a measurement of the 21+ state lifetime in the N=Z nucleus 74Rb. A novel technique called the Differential Recoil Distance Method was used to extract the lifetime from the gamma-ray spectra. The next-generation gamma-ray detector array GRETINA was used in the experiment, again coupled to the S800 Spectrograph to detect residues from 9Be(74Kr, 74Rb) charge exchange reactions. The B( E2;2+1→0+1) strength was calculated and is consistent with the measured strength of the transition between the isobaric analogue states in 74Kr, which may be a signature of shape coexistence in 74Rb.