Pauli Consistent $α$--$α$ Interaction from Inverse Scattering via Phase Function Wavefunctions and RGM Antisymmetrization

Abstract

The present study employs the phase function method (PFM) to construct scattering wavefunctions for the $α$--$α$ system, which is central to understanding the structure of $^{8}\mathrm{Be}$. The primary objective is to analyze scattering dynamics through the reconstruction of radial wavefunctions for the $\ell = 0$, 2, and 4 partial waves within the PFM framework, thereby avoiding direct numerical integration of the Schrödinger equation. Previously optimized single-term and two-term Morse potentials are used for benchmarking, while a double Gaussian (DG) potential is independently determined using a genetic algorithm. The resulting non-antisymmetrized wavefunctions are subsequently employed as input to the resonating group method (RGM), enabling the incorporation of Pauli exclusion effects. The antisymmetrized wavefunctions obtained in this manner show good agreement with earlier results reported by Hiura \textit{et al.} The quasi-bound state energy for the $\ell = 0$ partial wave is evaluated using the matrix method and is found to be consistent with the experimental value of $0.08,(0.09)$~MeV. The analysis further indicates the presence of two Pauli-forbidden S-wave states, consistent with Levinson's theorem, while the positive-energy solution near $0.08~\mathrm{MeV}$ corresponds to the physical $^{8}\mathrm{Be}$ resonance. Scattering parameters extracted from the proposed interactions are in good agreement with NLO, NNLO, and empirical results. Overall, the results establish the effectiveness of the PFM-based framework for reconstructing scattering observables and provide further support for the robustness of phenomenological $α$--$α$ interaction models.