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The 1/2+ state in the odd-A Bi isotopes is interpreted as an intruder shell model state with one hole in the s1/2 level just below the Z=82 closed shell. Likewise, the 9/2− state in the odd-A Tl isotopes is the intruder level corresponding to one proton in the otherwise empty shell above Z=82. These intruder states come quite low near the middle of the neutron shell and are observed as isomeric states. The positions of the intruding isomeric states as a function of the neutron number are important in understanding the shell model interactions producing the relative stability of the intruding states. In this region, the middle of the neutron shell is also quite far from stability, approaching the proton drip line, and hence, α emission is a dominant decay mode. In a series of α-decay fine structure measurements of Bi isotopes, the location of the s1/2 intruder level has been determined down to mass 187. The ground states of the odd-A At isotopes from 197At upward have been assigned a spin of 9/2−, but the ...

In order to test the feasibility of Coulomb excitation of radioactive projectiles with low beam energies and intensities, they have produced a secondary radioactive beam of {sup 78}Rb and Coulomb re-excited it. The beam was produced in the fusion evaporation reaction {sup 24}Mg({sup 58}Ni,3pn){sup 78}Rb at a beam energy of 260 MeV, using the Argonne National Laboratory ATLAS accelerator. The residues of interest were separated from other reaction products and non-interacting beam using the Fragment Mass Analyzer (FMA). The beam leaving the FMA was {sup 78}Kr and {sup 78}Rb{sup gs,m1,m2}, which was refocused onto a {sup 58}Ni secondary target. They have extracted a spectrum of {gamma}-rays associated with re-excitation of A = 78 isobars. The re-excitation of stable {sup 78}Kr was observed, which serves as a reference. Gamma-rays associated with excitation of {sup 78}Rb{sup gs,m1,m2} were also seen. The measured yields indicate that all the {sup 78}Rb states are highly deformed.

The {sup 16}O + {sup 58}Ni reaction was used to study yrast and non-yrast excitations in {sup 71}As, {sup 72}Se, and {sup 72}Br. High-spin yrast and negative-parity non-yrast bands were observed in {sup 72}Se. The F{sub 7/2} proton extruder orbital was identified in {sup 71}As. The odd-even staggering in the {pi}g{sub 9/2}{nu}g{sub 9/2} decoupled band in {sup 72}Br is compared with similar structures in heavier Br isotopes.