Investigation of heavy N∼Z nuclei using energetic radioactive ion beams

The experimental nuclear spectroscopic data for known nuclides of mass number 76 (Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr, Y) have been evaluated and presented together with Adopted properties for levels and γ rays. With the exception of structure data for ⁷⁶Ga nucleus, significant new data have been incorporated for all the other nuclides of A=76 since the previous 1995 update in ENSDF database and NDS publication 1995Si03. No data are yet available for excited states in ⁷⁶Fe, ⁷⁶Cu and ⁷⁶Y. Decay scheme characteristics for the decay of ⁷⁶Co, ⁷⁶Ni, and ⁷⁶Y are unknown while those for decays of ⁷⁶Cu and ⁷⁶Sr seem incomplete. For ⁷⁶Ni, very little structure data are available, and for ⁷⁶Ga and ⁷⁶As, only low-spin ($\text{J}<4$ or so) information is available. This work supersedes the data presented in the previous (1995Si03) NDS evaluation of A=76.

Nuclear spectroscopic information for known nuclides of mass number 74 (Co,Ni,Cu,Zn,Ga,Ge,As,Se,Br,Kr, Rb,Sr) with Z = 27 to 38 and N = 47 to 36 have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No excited state data are yet available for ⁷⁴Co, ⁷⁴Cu and ⁷⁴Sr. This evaluation supersedes previous full evaluations of A = 74 by 1987Si08 and 1976Ko07, and a midstream evaluation (published in update mode) by 1995Fa23 with a literature cutoff date of May 1994. Extensive new data have been included for most nuclides in the current revision of A = 74.

The Kr isotopes are considered to be among the best cases for shape coexistence studies in the mass $A\sim 70$ region. Our campaign to investigate in detail the development of the shape coexistence in the neutron deficient Kr isotopes was started with the stable nucleus ⁷⁸Kr. To obtain the information about the intrinsic shape, Coulomb excitation experiments were performed. A total of 26 matrix elements were determined for ⁷⁸Kr. Simple geometrical and algebraic models do not reproduce all details of the electromagnetic structure. A good interpretation of the complex structure of the nucleus with competing oblate and prolate shapes comes from a study within the complex EXCITED VAMPIR approximation using Hartree–Fock–Bogoliubov transformations with symmetry projection before variation. The measured matrix elements are compared with the predictions of this model.