Abstract
100Sn is the heaviest self-conjugate nuclei with the doubly-magic shell (N = Z = 50) while locates right on the proton drip-line. Therefore, its shell magicity needs to be carefully investigated to provide launching point for shell model and necessary information of nuclear forces in this region. However, large discrepancies are found in the level schemes of 100Sn calculated from different models [1], while previous experiments were only able to resolve the half-life of ground state [2, 3]. Additionally, the structure of 100Sn is crucial for understanding the mechanism of nucleosynthesis around A ≈ 100, N ≈ Z region as 100Sn is predicted as the end point of rp process [4].
An in-beam gamma measurement targeting the low-lying states (particularly the first 2+ state) of 100Sn will be performed at the RIBF facility in RIKEN Japan. A 124Xe beam will bombard upon a 9Be target at 345 MeV/u with an illumination of 140 pnA. Secondary beams and final products will be identified, event by event, by using the BigRIPS separator and ZeroDegree spectrometer, respectively. 100Sn will be produced from the bombardment of 101,102Sn secondary beams upon the MINOS system (a 30 mm thick liquid Hydrogen target with reaction vertex tracking ability), at around 215 MeV/u, through quasi-free (p, pn) and two neutron (p, p2n) knockout reactions, respectively. The deexcitation γ rays will be measured by DALI2+ detection array which provides superior detection efficiency. The level scheme of low-lying states of 100Sn will be measured. The energy of the first 2+ state from the measurement will directly indicate the N = Z = 50 shell magicity and assess different structure models. The results will also help establish a better understanding of the rp process.
Reference :
[1] Faestermann, T., M. Górska, and H. Grawe, The structure of 100Sn and neighbouring nuclei. Progress in particle and nuclear physics, 2013. 69: p. 85-130.
[2] Hinke, C.B., et al., Superallowed Gamow-Teller decay of the doubly magic nucleus 100Sn. Nature, 2012. 486(7403): p. 341-345.
[3] Lubos, D., et al., Improved Value for the Gamow-Teller Strength of the 100Sn Beta Decay. Physical review letters, 2019.
[4] Schatz, H., et al., End point of the rp process on accreting neutron stars. PHYS REV LETT, 2001. 86(16): p. 3471-3474.
Anyone interested is welcome to attend.