Abstract
Intense and purified radioactive beam of post-accelerated $^{14}$O was used to study the low-lying states in the unbound $^{15}$F nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at E$\_R$=4.757(6)(10)~MeV with a width of $\Gamma$=36(5)(14)~keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a $^{12}$C core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the $2s\_{1/2}$ shell.
Highlights
The boundaries for nuclear stability against particle emission are called “drip lines”
It is very similar to those obtained in Refs. [14,17,18], but with a much higher statistics, improved energy resolution and covering a larger energy range
An analysis of the excitation function using the R-Matrix method was performed with the code AZURE2 [33]
Summary
The boundaries for nuclear stability against particle emission are called “drip lines”. If the spacing between the resonances becomes smaller than their widths, the salient reordering processes under the influence of the environment of continuum states take place. Direct studies of resonance trapping are not feasible because one cannot trace widths of states as a function of the coupling strength to continuum. Much information have been accumulated indirectly which contradict the naive expectation based on the random matrix theory that all nuclear levels will be broadened with increasing coupling strength to the continuum [8]
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