Spectroscopic study of neutron shell closures via nucleon transfer in the neardripline nucleus 23O.
ABSTRACT Neutron single particle energies have been measured in 23O using the 22O(d,p)23O*>22O+n process. The energies of the resonant states have been deduced to be 4.00(2) MeV and 5.30(4) MeV. The first excited state can be assigned to the nu d3/2 single particle state from a comparison with shell model calculations. The measured 4.0 MeV energy difference between the nu s1/2 and nu d3/2 states gives the size of the N=16 shell gap which is in agreement with the recent USD05 ("universal" sd from 2005) shell model calculation, and is large enough to explain the unbound nature of the oxygen isotopes heavier than A=24. The resonance detected at 5.3 MeV can be assigned to a state out of the sd shell model space. Its energy corresponds to a approximately 1.3 MeV sized N=20 shell gap, therefore, the N=20 shell closure disappears at Z=8 in agreement with Monte Carlo shell model calculations using SDPFM interaction.

Article: βDecay of Light NeutronRich Nuclei
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ABSTRACT: The βdecays of neutronrich carbon, nitrogen and fluorine isotopes have been systematically studied using the OXBASH shell Model. In the psd, spsd and spsdpf model space, we use the WBP interaction to calculate the halflives and neutron emission probabilities of neutronrich carbon and nitrogen isotopes, respectively. With the USD (W) and CW interactions, we calculate the halflives and neutron emission probabilities of neutronrich fluorine isotope in the sd model space, respectively. The calculated halflives and neutron emission probabilities reproduce recent experimental data very well. It seems to show that the particles of the neutronrich carbon and nitrogen isotopes are mainly excited in the spsd space. The βdecay of 21N to the neutron bound states in 21O is mostly the first forbidden transition which makes the neutron emission probability increase. The theoretical calculation of βdecay of 25F to 25Ne with CW interaction shows that CW interaction is better than USD interaction.Plasma Science and Technology 07/2012; 14(7):610613. DOI:10.1088/10090630/14/7/10 · 0.60 Impact Factor 
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ABSTRACT: The spectroscopy of O21 has been investigated using a radioactive O20 beam and the (d,p) reaction in inverse kinematics. The ground and first excited states have been determined to be Jpi=5/2+ and 1/2+, respectively. Two neutron unbound states were observed at excitation energies of 4.77(10) and 6.17(11) MeV. The spectroscopic factor deduced for the lower of these, interpreted as a 3/2+ level, reveals a relatively pure (60%) 0d3/2 singleparticle configuration, in good agreement with shellmodel calculations that predict O26 to be unbound. The large energy difference between the 3/2+ and 1/2+ states is indicative of the emergence of the N=16 shell gap, which is estimated to be 5.1(11) MeV. For the higherlying resonance, which has a character consistent with a spinparity assignment of 3/2+ or 7/2, a 0.71(22) branching ratio to the first 2+ state in O20 has been observed.Physical Review C 01/2011; 84. DOI:10.1103/PhysRevC.84.011301 · 3.88 Impact Factor 
Article: Nonperturbative ShellModel Interactions from the InMedium Similarity Renormalization Group
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ABSTRACT: We present the first ab initio construction of valencespace Hamiltonians for mediummass nuclei based on chiral two and threenucleon interactions using the inmedium similarity renormalization group. When applied to the oxygen isotopes, we find good agreement with experimental ground state energies, including the flat trend beyond the drip line at 24O. Similarly, evenparity spectra in 21,22,23,24O are in excellent agreement with experiment, and we present predictions for excited states in 25,26O. The results exhibit a weak dependence on the harmonicoscillator basis parameter and give a good description of spectroscopy within the standard sd valence space.Physical Review Letters 10/2014; 113:142501. DOI:10.1103/PhysRevLett.113.142501 · 7.73 Impact Factor