Background: Detailed experimental knowledge of the level structure of light weakly bound nuclei is necessary to guide the development of new theoretical approaches that combine nuclear structure with reaction dynamics.

Purpose: The resonant structure of ${}^8$B is studied in this work.

Method: Excitation functions for elastic and inelastic ${}^7$Be+$p$ scattering were measured using a ${}^7$Be rare isotope beam. Excitation energies ranging between 1.6 and 3.4 MeV were investigated. An $R$-matrix analysis of the excitation functions was performed.

Results: New low-lying resonances at 1.9, 2.54, and 3.3 MeV in ${}^8$B are reported with spin-parity assignment 0${}^{+}$, 2${}^{+}$, and 1${}^{+}$, respectively. Comparison to the time-dependent continuum shell (TDCSM) model and ab initio no-core shell model/resonating-group method (NCSM/RGM) calculations is performed. This work is a more detailed analysis of the data first published as a Rapid Communication. J. P. Mitchell, G. V. Rogachev, E. D. Johnson, L. T. Baby, K. W. Kemper et al., [Phys. Rev. C 82, 011601(R) (2010)].

Conclusions: Identification of the 0${}^{+}$, 2${}^{+}$, 1${}^{+}$ states that were predicted by some models at relatively low energy but never observed experimentally is an important step toward understanding the structure of ${}^8$B. Their identification was aided by having both elastic and inelastic scattering data. Direct comparison of the cross sections and phase shifts predicted by the TDCSM and ab initio no-core shell model coupled with the resonating group method is of particular interest and provides a good test for these theoretical approaches.

• Received 1 March 2013

DOI:https://doi.org/10.1103/PhysRevC.87.054617