J. P. Mitchell

Resonance scattering and α‐transfer reactions for nuclear astrophysics

Resonances in atomic nuclei play a vital role in determining rates of astrophysically important nuclear reactions. Efficient experimental technique, Thick Target Inverse Kinematics method, which allows to study properties of resonances in exotic nuclei with radioactive beams using resonance elastic scattering is discussed. Various extensions of this technique for measurements of inelastic excitation functions and application of one of these methods for 7Be(p,p’)7Be* (0.43 MeV) reaction is considered.The astrophysical rates of some (α, γ), (α, n), (α, p) reactions are often determined by the near α‐threshold resonances. Application of sub‐Coulomb α‐transfer reactions (7Li,t) and (6Li,d) allow to determine α‐particle Asymptotic Normalization Coefficients of these resonances with minimal dependance on model parameters. The 14C(α,γ) reaction is considered as an example for application of this approach.

14C(α,γ) reaction rate

The 14C(alpha,gamma) reaction rate at temperatures below 0.3 GK depends on the properties of two near threshold resonances in 18O, the 1- at 6.198 MeV and the 3- at 6.404 MeV. The alpha+14C Asymptotic Normalization Coefficients (ANCs) for these resonances were determined using the alpha-transfer reactions 14C(7Li,t) and 14C(6Li,d) at sub-Coulomb energies. The 14C(alpha,gamma) reaction rate at low temperatures has been evaluated. Implications of the new reaction rate on the evolution of accreting helium white dwarfs and on the nucleosynthesis of low mass stars during the asymptotic giant branch (AGB) phase are discussed.

Low-lying states in 8B

Excitation functions of elastic and inelastic 7 Be + p scattering were measured in the energy range between 1.6 and 2.8 MeV in the c.m. An R-matrix analysis of the excitation functions provides strong evidence for new positive parity states in 8 B. A new 2 + state at an excitation energy of 2.55 MeV was observed, and a new 0 + state at 1.9 MeV is tentatively suggested. The R-matrix and time-dependent continuum shell model were used in the analysis of the excitation functions. The new results are compared to the calculations of contemporary theoretical models.

Structure of 8 B from elastic and inelastic 7 Be+ p scattering

Motivation: 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, 2.5, 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, 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.

Structure of8B from elastic and inelastic7Be+pscattering

Motivation: 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, 2.5, 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, 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.

Structure of 8B from elastic and inelastic 7Be+p scattering

Motivation: 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, 2.5, 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, 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.

Structure of light nuclei in resonance scattering experiments

Resonance scattering with rare isotope beams provides direct access to continuum properties of exotic nuclei and can serve as a stringent test for modern theoretical approaches. Properties of neutron deficient isotope 8B, that were studied using resonance scattering of protons of 7Be, are discussed and compared to the predictions of the ab initio theories. New experimental data on clustering in 10Be studied using 6He+α resonance elastic scattering is presented.

Low-lying states in B 8

Excitation functions of elastic and inelastic 7 Be + p scattering were measured in the energy range between 1.6 and 2.8 MeV in the c.m. An R-matrix analysis of the excitation functions provides strong evidence for new positive parity states in 8 B. A new 2 + state at an excitation energy of 2.55 MeV was observed, and a new 0 + state at 1.9 MeV is tentatively suggested. The R-matrix and time-dependent continuum shell model were used in the analysis of the excitation functions. The new results are compared to the calculations of contemporary theoretical models.

Low-lying states inB8

Excitation functions of elastic and inelastic 7 Be + p scattering were measured in the energy range between 1.6 and 2.8 MeV in the c.m. An R-matrix analysis of the excitation functions provides strong evidence for new positive parity states in 8 B. A new 2 + state at an excitation energy of 2.55 MeV was observed, and a new 0 + state at 1.9 MeV is tentatively suggested. The R-matrix and time-dependent continuum shell model were used in the analysis of the excitation functions. The new results are compared to the calculations of contemporary theoretical models.