Lifetime measurements in 99Nb and 99Zr: Investigation of shape coexistence

The A approximate to 100 mass region is of special interest due to a rapid shape transition, observed by going from neutron number 58 to 60, especially pronounced in the Zr isotopes, where 98Zr is weakly and100Zr is strongly deformed. To further examine this intricate phenomenon, in this work lifetimes of low-lying excited states in the nuclei 99Zr and 99Nb were determined using fast-timing techniques and an experimental setup consisting of four LaBr3(Ce) detectors. Neutron rich A = 99 fragments were produced in neutron induced fission and separated by the spectrometer LOHENGRIN at the Institut Laue-Langevin in Grenoble, France. Experimental values are compared to two different calculations in the framework of the interacting boson-fermion model and discussed in the context of shape coexistence.

Automated summary

The rapid shape transition observed in the A approximate to 100 mass region, particularly in Zr isotopes, has attracted special interest. In this study, the lifetimes of low-lying excited states in 99Zr and 99Nb nuclei were determined using fast-timing techniques and experimental setup. The experimental values were compared to calculations from the interacting boson-fermion model and discussed in the context of shape coexistence.