Direct and sequential processes in the 16O(7Li, 7Be)16N reaction

doi:10.1016/0375-9474(86)90287-3

Nuclear Physics A

Volume 458, Issue 1, 29 September 1986, Pages 137-156

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Abstract

Calculations are presented for the ¹⁶O(⁷Li, ⁷Be)¹⁶N charge exchange reaction. For the direct reaction, the tensor interaction leads to form factors with large spin and angular momentum transfer which are important for the unnatural parity states. The (⁷Li, ⁶Li)(⁶Li,⁷Be) sequential process exhibits a strong J-dependence and is the dominant contribution to the natural parity states.

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Shedding light on nuclear aspects of neutrinoless double beta decay by heavy-ion double charge exchange reactions
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We review the status and prospects of heavy-ion double charge exchange (HI-DCE) reactions. Their important role for nuclear reaction, nuclear structure and double beta-decay investigations is outlined. From the experimental side the characteristically tiny cross sections for these processes and the high background generated by other more probable competing reactions is the main challenge, which has hindered HI-DCE spectroscopy until recent years. Modern magnetic spectrometers have proven to possess the right requisites to overcome past limitations, fostering the present and future development of the field. From the theory side, the description of the measured HI-DCE cross sections poses manifold challenges. Dealing with processes which involve composite nuclei, HI-DCE reactions can, in principle, proceed through several alternative paths. These, in turn, correspond to different reaction mechanisms probing competing aspects of nuclear structure, from mean field to various classes of nucleon–nucleon interactions and correlations. A powerful way to scrutinize the nuclear response to HI-DCE is to consistently link it to the information extracted from the competing direct reactions. Indeed, these complementary studies are mandatory in order to minimize the systematic errors in the data analyses and build a many-facets and parameter-free representation of the systems under study.
Heavy ion charge exchange reactions as probes for nuclear β-decay
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The status and prospects of heavy ion charge exchange reactions are reviewed. Their important role for nuclear reaction, nuclear structure, and beta-decay investigations is emphasized. Dealing with peripheral reactions, direct reaction theory gives at hand the proper methods for single (SCE) and double charge exchange (DCE) ion–ion scattering. The microscopic descriptions of charge exchange ion–ion residual interactions and the reaction mechanism are obtained by distorted wave theory. Ion–Ion optical potentials and reaction form factors are determined in a folding approach by using NN T-matrices and microscopic ground state and transition densities, respectively. The theory of one-step direct and two-step transfer reaction mechanisms for SCE reactions is discussed and illustrated in applications to data. Specific SCE reactions are discussed in detail, emphasizing the versatility of projectile–target combinations and incident energies. SCE reactions induced by $^{12} C$ and $^{7}$ Li beams are presented as representative examples. Heavy ion DCE reactions are shown to proceed in principle either by sequential pair transfer or two kinds of collisional NN processes. Double single charge exchange (DSCE) is given by two consecutive SCE processes, resembling in structure $2 ν 2 β$ decay. A competing process is a two-nucleon mechanism, relying on short range NN correlations and leading to the correlated exchange of two charged mesons between projectile and target. These Majorana DCE (MDCE) events are of a similar diagrammatic structure as $0 ν 2 β$ decay. The similarities of the DSCE and MDCE processes to pionic DCE reactions are elucidated. An overview on recent experimental research activities on heavy ion DCE research is given. Charge exchange strength distributions above the isovector spin-multipole resonance region and the excitation of nucleon resonances in high energy heavy ion SCE reactions are discussed in connection with the quenching issue.
Elastic and inelastic scattering of 15N ions by 7Li at 81 MeV versus that of 14N ions by 7Li at 80 and 110 MeV
2017, Nuclear Physics A
Citation Excerpt :
In addition to the CDCC method Li induced reactions have been used to determine the role of strongly coupled reaction routes on elastic scattering as well as charge exchange reactions through the Coupled Reaction Channels (CRC) method. Excellent examples of these studies are that of 16O(7Li, 7Be) [12] and 11B(7Li, 7Be) [13] where direct and two step cluster transfers were explored. The cluster spectroscopic amplitudes such as those obtained within the invariant shell model [14] are now available allowing these various transfer routes to be explored in detail as done in the present work.
Angular distributions of the elastic and inelastic scattering of ¹⁵N ions by ⁷Li nuclei were measured at the energy $E_{lab} ({}^{15}N) = 81 MeV (E_{c.m.} = 25.77 MeV)$ . The data were analyzed within the coupled-reaction-channels method. The elastic and inelastic scattering, spin reorientations of ⁷Li as well as the more important one- and two-step transfer reactions were included in the channels-coupling scheme. The parameters of ${}^{7}{Li} + {}^{15}N$ optical potential of Woods–Saxon form as well as deformation parameters of these nuclei were deduced. The analysis showed that the forward angle elastic scattering is dominated by pure potential scattering whereas the middle and large angle scattering gets a contribution from the ground state reorientation of ⁷Li. Contributions from particle transfers were negligible for the present scattering system. The ${}^{7}{Li} + {}^{15}N$ elastic scattering was compared with that of ${}^{7}{Li} + {}^{14}N$ at the energies $E_{lab} ({}^{14}N) = 80 MeV$ and 110 MeV. Different contributions to the elastic scatterings from other nuclear processes are shown to be responsible for the isotopic difference observed in the large angle scattering.
Analysis of the 11B(7Li,7Be) 11Be reaction at 57 MeV in a microscopic approach
2004, Nuclear Physics A
The ¹¹B(⁷Li, ⁷Be)¹¹Be charge exchange reaction has been studied at an incident energy of 57 MeV. Spectra were measured at forward angles, θ_cm⩽35°. The good energy resolution (∼50 keV) allowed the identification of transitions both to the ⁷Be (3/2⁻, gs) and ⁷Be(1/2⁻, 429 keV) exit channels and hence the direct measurement of the ratio of the respective cross sections and angular distributions. Besides the bound ground and first excited state of ¹¹Be several low lying excitations just above the neutron threshold are observed. A structure seen at $E^{∗} =9.4$ MeV with FWHM ∼7 MeV is compatible with the spin dipole resonance (SDR). The data are analysed in a many-body approach. For the projectile transitions shell model results are used. In order to account properly for the special features of the weakly bound ¹¹Be system the target transitions are described microscopically by Hartree–Fock–Bogoliubov (HFB) and quasi-particle random phase approximation (QRPA) theory. The HFB ground state densities and the QRPA transition densities, respectively, are used in folding calculations for the optical potentials and transition form factors. Spectra and β-decay transitions strengths are reasonably well described. The measured cross section are well reproduced by one-step direct charge exchange distorted wave born approximation (DWBA) calculations. A dominance of unnatural parity transitions is found. This is explained in terms of the spin transfer behaviour of the nucleon–nucleon isovector interaction at low bombarding energy.
Energy levels of light nuclei A = 5, 6, 7
2002, Nuclear Physics A
Energy levels of light nuclei A = 16-17
1993, Nuclear Physics, Section A

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Nuclear Physics A

Abstract

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Cited by (21)

Shedding light on nuclear aspects of neutrinoless double beta decay by heavy-ion double charge exchange reactions

Heavy ion charge exchange reactions as probes for nuclear β-decay

Elastic and inelastic scattering of <sup>15</sup>N ions by <sup>7</sup>Li at 81 MeV versus that of <sup>14</sup>N ions by <sup>7</sup>Li at 80 and 110 MeV

Analysis of the <sup>11</sup>B(<sup>7</sup>Li,<sup>7</sup>Be) <sup>11</sup>Be reaction at 57 MeV in a microscopic approach

Energy levels of light nuclei A = 5, 6, 7

Energy levels of light nuclei A = 16-17