Abstract
The main goal of nuclear physics is to understand the origin of elements. While the three most solar abundance peaks are reasonably understood, the element abundance around mass number ~160 (between the 2nd and 3rd main peak) is still a puzzle[1, 2, 3]. Improved calculation for the rapid-neutron capture process (so-called r-process) requires the experimental data on β-decay half-lives and nuclear deformation (latter derived from energy level scheme)[2,3], particularly for the well deformed nuclei, such as 173,174Ho (Z=67, N=106,107) and 173,174Er (Z=68, N=105,106).
We therefore performed β-decay spectroscopy experiment of 173Ho -> 173Er and 174Ho -> 174Er at Radioactive Ion Beam Factory (RIBF) in RIKEN using in-flight fission of 238U beam. Silicon detector array (WAS3Abi) and gamma-detector array (EURICA) were used to measure heavy ions, β particles and γ rays. β decay half-lives of 173Ho and 174Ho were determined to be 7.0(7) s and 3.4(10) s respectively. Also, a new low-lying isomeric state at 405 keV with half-life of 3.7(12) μs was discovered in 173Ho. Furthermore, based on the systematics of N=106 isotones, the newly observed energy level 1311 keV in 174Er was assigned to be Jπ=9-. Together with the extracted logft values to Jπ =8- and 9- states in 174Er , the spin-parity of ground state in 174Ho could be constrained as Jπ=8-. In addition, five gamma-transitions were observed in 173Er, and a scheme of three low-lying energy levels was therefore deduced. These experimental results are useful input for the r-process calculation. In this talk, experimental setup and results will be presented.
References:
[1] R. Surman et al., Phys. Rev. Lett. 79, 1809 (1997)
[2] Matthew R. Mumpower, Gail C. McLaughlin, and Rebecca Surman,Phys. Rev. C 86, 0358039(2012)
[3] Matthew R. Mumpower, G. C. McLaughlin, and Rebecca Surman,Phys. Rev. C 85, 045801(2012)
Anyone interested is welcome to attend.