Unbound neutron ν0d3/2 strength in 17C and the N=16 shell gap

Le résumé fourni par la source

Significant continuum strength has been observed to be populated in 17 C produced in the d( 16 C,p) reaction at a beam energy of 17.2 MeV/nucleon. The strength appears at greater than ∼2 MeV above the single-neutron decay threshold and has been identified as arising from transfer into the neutron 0 d 3 / 2 orbital. Guided by shell model predictions the greater majority of the strength is associated with a 3/2 + state at an excitation energy of 4.40 − 0.14 + 0.33 MeV and a much weaker 3/2 + level at 5.60 − 0.45 + 1.35 MeV. The corresponding total widths were determined to be 3.45 − 0.78 + 1.82 and 1.6 − 1.4 + 4.6 MeV, respectively. From the backward angle proton differential cross sections and the branching ratios for neutron decay to the 16 C(2 1 + ) level, the corresponding spectroscopic factors to the ground state were deduced to be 0.47±10 and <0.09. Shell-model calculations employing the phenomenological SFO-tls interaction as well as Gamow Shell-Model calculations including continuum effects are in reasonable agreement with experiment, although the predicted strength lies at somewhat lower energy. The size of the N=16 shell gap ( ε ν 0 d 3 / 2 − ε ν 1 s 1 / 2 ) was estimated to be 5.08 − 0.33 + 0.43 MeV - some 1.3 MeV larger than found in the SFO-tls shell model calculation.

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