An above-barrier narrow resonance in $^{15}$F

TL;DR

This study precisely measured a new narrow resonance state in the unbound nucleus $^{15}$F using radioactive beams and resonant scattering, and analyzed its structure with advanced shell model calculations.

Contribution

It reports the first high-precision measurement of the second excited state in $^{15}$F and investigates its structure with the Gamow Shell Model, revealing a nearly pure two-proton wave function.

Findings

Resonance at E_R=4.757 MeV with a width of 36 keV measured for the first time.

The state is predominantly a two-proton configuration in the 2s_{1/2} shell.

Provides insights into the structure of nuclei beyond the proton drip line.

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.