The Core of $^{25}$F in the Rotational Model

TL;DR

This paper investigates the structure of $^{25}$F using the Particle-Rotor Model, interpreting recent experimental data to understand its core properties, rotational behavior, and single-particle strength fragmentation.

Contribution

It applies the Particle-Rotor Model to interpret experimental results on $^{25}$F, revealing its rotational structure and core deformation, which is a novel approach for this nucleus.

Findings

Effective core of $^{25}$F differs from free $^{24}$O

Estimated $2^+$ energy of core at approximately 3.2 MeV

Moderate quadrupole deformation of about 0.15

Abstract

In a recent experiment, carried out at RIBF/RIKEN, the $^{25}$F$(p,2p)$$^{24}$O reaction was studied at 270 MeV/A in inverse kinematics. Derived spectroscopic factors suggest that the effective core of $^{25}$F significantly differs from a free $^{24}$O nucleus. We interpret these results within the Particle-Rotor Model and show that the experimental level scheme of $^{25}$F can be understood in the rotation-aligned coupling scheme, with its $5/2^+_1$ ground state as the band-head of a decoupled band. The excitation energies of the observed $1/2_1^+$ and $9/2_1^+$ states correlate strongly with the rotational energy of the effective core, seen by the odd proton, and allow us to estimate its $2^+$ energy at $\approx$ 3.2 MeV and a moderate quadrupole deformation, $\epsilon_2 \approx 0.15$. The measured fragmentation of the $\pi d_{5/2}$ single-particle strength is discussed and some further experiments suggested.