Investigation on shape transitions and shape coexistences in neutron-rich odd-A and odd-odd nuclei around 100Zr

点击翻译按钮获取中文摘要

The proposal aims to provide new and improved spectroscopic information on odd-A and odd-odd nuclei in the vicinity of 100Zr mainly by lifetime measurements of low-energy excited states using fast-timing techniques. The goal is to obtain more spectroscopic evidences for the evolution of the neutron and proton single-particle orbitals in this particular mass region. The deduced gamma-ray transition rates will be compared with predictions using analytic collective models based on microscopically derived energy-density functionals which are able to describe the spherical-to-deformed shape transition and shape-coexistence phenomena observed in the vicinity of N = 60 isotones close to 100Zr. The candidates of interest to be measured are the even-odd 101Mo, the odd-even 103Tc and the odd-odd 102Tc nuclei. Other experimental data on the odd-even 99Y nucleus and the N = 59 odd-odd 98Y and 100Nb isotones have recently been acquired and requires to be analyzed. The neutron-rich candidates to be measured are well produced in thermal-neutron induced fission of, e.g. 235U. The experiments will be performed at the “Lohengrin” fission-fragment separator of the Institut Laue-Langevin (ILL) in Grenoble, France. In collaboration with the ILL and other international scientists, 3-4 fast-timing campaigns will be organized by the IKP. The IKP Köln high-performance LaBr3(Ce) detectors will be used for picosecond-sensitive lifetime determination with low-energy gamma rays via gamma-gamma or beta-gamma time-difference measurements. Installation, calibration and surveillance of the experiment will be done by the IKP fast-timing group. The experimental data will be analyzed on the high-speed IKP server using software specially compatible to the ILL data format and optimized for fast-timing analyzes. The new and improved lifetime results obtained will be used to calculate B(E2) and B(M1) transition rates for investigation on collectivity or for being used as input parameters to perform more phenomenological nuclear structure calculations. The new calculations within the framework of the Interacting-Boson-Fermion (-Fermion) model will be performed by theoretical nuclear structure physicists with whom we are successfully collaborating for many years. Our major objective is to obtain an improved insight on the evolution of shape transition and shape coexistence in nuclei close to 100Zr as a function of the proton and neutron number (orbitals) and to publish results and theoretical interpretations.