Direct empirical correlation between proton-neutron interaction strengths and the growth of collectivity in nuclei

A direct correlation between experimental values of proton-neutron interaction strengths and experimental measures of the growth of collectivity in nuclei is found. In particular, differences in the p-n interaction strengths and differences in growth rates of collectivity in particle-particle (or hole-hole) and particle-hole regions are found to correspond

Proton-neutron interactions and the new atomic masses

Double differences of masses can be used to isolate specific nucleonic interactions. With the new 2003 mass tabulation a significant increase in the number of empirical average proton-neutron interactions of the last nucleons can be extracted. It is shown that they exhibit dramatic and distinctive patterns, especially near doubly magic nuclei, that these patterns can be interpreted with a simple ansatz based on overlaps of proton and neutron orbits, and that the trends in p-n interactions across entire shells can be understood if they are correlated with the fractional shell filling. It is shown how these empirical interactions can be sensitive to changes in shell structure in exotic nuclei. Finally, these results are used to suggest criteria for future mass measurements with new exotic beam facilities

Investigation into the B(E2) anomaly in Nd144 using Coulomb excitation

The ratio of B(E2) strengths between the lowest lying members of the ground state band in Nd144, B4/2=B(E2;41+→21+)/B(E2;21+→01+), which is used to quantify collectivity in nonmagic nuclei, has been remeasured by means of Coulomb excitation. Ambiguities in literature values for this ratio have been resolved. The results are discussed in terms of the interplay of collective and single-particle degrees of freedom, and in the context of the formation of collective structures in the A=140 mass region, and more generally near (sub)shell closures. In addition, the B4/2 ratio of Sm148 has been remeasured, and the quadrupole moment of the 41+ state is found to be on the order of 1eb. © 2008 The American Physical Society

Recoil-ion trapping for precision mass measurements

status: publishe

Transition from the seniority regime to collective motion

B(E2) values from isomeric states near closed shells are discussed in the context of the behavior of seniority conserving transitions induced by even tensor operators. This result provides a signature for the transition from the seniority regime to collective motion that can be of use in identifying shell structure in exotic nuclei

Isomer and in-beam spectroscopy of medium-spin states in Zr-91,Zr-92

Near-yrast states have been identified in the stable Zr-91,Zr-92 isotopes using the fusion evaporation reaction Se-82(C-13,xn)Zr95-x at an incident beam energy of 50 MeV. Gamma-ray spectroscopy of states above the reported tau = 6 mu s, I-pi=(21)/(+)(2) isomer in Zr-91 are reported for the first time with consequences for stimulating new shell model calculations which incorporate either the breaking of the N=50 shell closure and/or the inclusion of the negative parity h(11/2) neutron intruder orbital

Isomer and in-beam spectroscopy of medium-spin states in ^91,92Zr

Near-yrast states have been identified in the stable 91,92Zr isotopes using the fusion evaporation reaction 82Se( 13C,xn)95-xZr at an incident beam energy of 50 MeV. Gamma-ray spectroscopy of states above the reported τ = 6 μs, I π=212+ isomer in 91Zr are reported for the first time with consequences for stimulating new shell model calculations which incorporate either the breaking of the N=50 shell closure and/or the inclusion of the negative parity h11/2 neutron intruder orbital. © 2006 American Institute of Physics