九大原子核セミナー

九州大学の原子核理論と原子核実験の共同開催のセミナー

第952回九大原子核セミナー

2018年11月27日(火) 16:30〜18:00

講師: Miguel Maeques 氏 (GANIL)
演題:First observation of the heaviest Boron and Nitrogen isotopes
場所:ウェスト1号館7階 物理セミナー室3 (W1-A-723室)

概要:
The well-established shell structure of the nucleus, that translates into an enhanced stability for systems with a magic number of protons and/or neutrons (2, 8, 20...), is distorted when nuclei approach the landscape limits or driplines, specially the more distant one, the neutron dripline. The most spectacular effect is found at neutron number N=16, in what is known as the oxygen anomaly: while oxygen can hold at most 16 neutrons, the next element, fluorine, can hold up to 22. In this respect, the neutron-rich tail of the boron and nitrogen isotopic chains are of particular importance. 21B is the first isotope beyond the dripline at N=16, and 24,25N represent one step further from the already exotic isotopes 25,26O.
In this seminar we will review the results from experiments performed at the Radioactive Isotope Beam Factory (RIBF) of the RIKEN Nishina Center, in which the most neutron-rich boron and nitrogen isotopes to date, 20,21B and 24,25N, have been observed for the first time using invariant-mass spectroscopy following one- or two-proton removal reactions from, respectively, 22N, 22C and 26,27F at energies around 230 MeV/nucleon. Their unbound nature lead to the decay into 19B or 23N plus one or two neutrons. Through a comparison with shell-model calculations and extrapolated values from mass evaluations, the results will be discussed in terms of the prevalence of the N=16 shell gap at Z<8.


q952.pdf
- | - | -
Calendar
Categories
New Entries
Recommend
Archives
Profile
Other