0000000000172017
AUTHOR
A. De Smet
Beta-decay measurements of neutron-rich thallium, lead, and bismuth by means of resonant laser ionisation
Abstract Neutron-rich thallium, lead, and bismuth isotopes were investigated at the ISOLDE facility. After mass separation and resonant laser ionisation of the produced activity, new spectroscopic data were obtained for 215,218 Bi and 215 Pb. An attempt to reach heavy thallium had to be abandoned because of a strong francium component in the beam that gave rise to a neutron background through (α,n) reactions on the aluminium walls of the experimental chamber.
β−decay of the neutron-rich isotope215Pb
This Brief Report reports on the first observation of the β--delayed γ decay of 215Pb, feeding states in 215Bi. The 215Pb beam was produced using resonant laser ionization and mass separated at the ISOLDE-CERN on-line mass separator. This ensured clean identification of the γ rays as belonging to the decay of 215Pb or its β-decay daughters. A half-life of 147(12) s was measured for the 215Pb β decay and a level scheme for the daughter nucleus 215Bi is proposed, resulting in an extended systematics of the excited states of the neutron-rich Bi isotopes.
First observation of the β-decay of neutron-rich 215Pb and 218Bi by the pulsed-release technique and resonant laser ionisation
The neutron-rich Tl, Pb and Bi isotopes are of exceptional interest to trace the evolution of single-particle levels away from the doubly magic 208Pb towards the neutron-rich side of the nuclear chart. While 208Pb is well understood in terms of the shell model, experimental data on the heavier isotopes is very scarce and it is far from clear to what extent the shell model is upheld [1]. Furthermore, large branchings ratios for β-delayed neutron emission are expected in this mass region, adding astrophysical interest to the subject [2].