Comparison of ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ and ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ elastic scattering: The role of ground state reorientation and breakup

Angular distributions of the differential cross section for elastic scattering and ${}^6\mathrm{Li}\to \alpha +d$ resonant breakup in the ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ system were measured in inverse kinematics with a 51-MeV ${}^{10}\mathrm{B}$ beam. A comparison with existing data for the ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ system at the same incident ${}^{10}\mathrm{B}$ energy revealed an important difference in the backward angle elastic scattering, with that for ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ being significantly larger in magnitude. A series of coupled channel and coupled discretized continuum channel calculations investigated the influence of ${}^{10}\mathrm{B}$ and ${}^7\mathrm{Li}$ ground state reorientation and breakup couplings on the elastic scattering. Elastic transfer of a ${}^4\mathrm{He}$ and ${}^3\mathrm{He}$ cluster between the ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ cores, respectively, was also investigated. Although a conclusive explanation of the observed difference in the backward angle elastic scattering between the two systems was not obtained, the elastic transfer mechanism could be definitively ruled out as a significant factor and there were indications that a difference in the effect of the breakup coupling may play a role even in these light systems. The ground state reorientation coupling in ${}^7\mathrm{Li}$, while exhibiting an interesting interference effect with the ${}^{10}\mathrm{B}$ ground state reorientation, was also found to make a negligible contribution to the difference in backward angle elastic scattering.

Figure 1

Typical residual $E$ spectra for detection of ${}^{10}\mathrm{B}$ (a) and ${}^6\mathrm{Li}$ (b) at an incident energy of $E_{\mathrm{lab}}({}^{10}\mathrm{B}$) = 51 MeV after the subtraction of background from multiparticle reactions. The curves denote symmetric Gaussian fits to the peaks.

Figure 2

Comparison of ${}^{10}\mathrm{B}+{}^{6,7}\mathrm{Li}$ elastic scattering data for an incident ${}^{10}\mathrm{B}$ energy of 51 MeV. The filled circles denote the ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ data obtained in this work and the open circles those of Kemper et al. [2]. The ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ data of Rudchik et al. [1] are denoted by the shaded squares. The solid and dashed curves are the results of OM calculations with the ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ and ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ potential parameters listed in Table 1, respectively.

Figure 3

(a) The present 51-MeV ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ elastic scattering data (filled circles) compared to the result of a CC fit including ${}^{10}\mathrm{B}$ ground state reorientation coupling (solid curve). The dotted curve denotes the effect of switching off the ${}^{10}\mathrm{B}$ reorientation coupling. (b) The 51-MeV ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ elastic scattering data of Rudchik et al. [1] (filled circles) compared to the result of a CC fit including ${}^{10}\mathrm{B}$ ground state reorientation coupling (solid curve). The dotted curve denotes the effect of switching off the ${}^{10}\mathrm{B}$ reorientation coupling. The dashed curve denotes the effect of including the ${}^7\mathrm{Li}({}^{10}\mathrm{B},{}^7\mathrm{Li}){}^{10}\mathrm{B}$ elastic transfer coupling using the spectroscopic amplitudes of Ref. [1].

Figure 4

The 51-MeV ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ elastic scattering data of Rudchik et al. [1] (filled circles) compared to the result of a CC fit including both ${}^7\mathrm{Li}$ and ${}^{10}\mathrm{B}$ ground state reorientation couplings (solid curve). The dotted curve denotes the effect of switching off both couplings. The dashed and dot-dashed curves denote the separate effects of the ${}^{10}\mathrm{B}$ and ${}^7\mathrm{Li}$ reorientation couplings, respectively.

Figure 5

Comparison of the results of CDCC calculations with the 51-MeV ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ elastic scattering data. The filled circles denote the data obtained in this work and the open circles those of Kemper et al. [2]. The solid curve denotes the full calculation, including the nonresonant continuum, and the dotted curve the no-coupling result.

Figure 6

Comparison of the results of CDCC calculations with the 51-MeV ${}^{10}\mathrm{B}+{}^6\mathrm{Li}$ differential cross section data for ${}^6\mathrm{Li}\to \alpha +d$ breakup via the three $L=2$ resonant states of ${}^6\mathrm{Li}$: (a) the 2.19-MeV $3^{+}$, (b) the 4.31-MeV $2^{+}$, and (c) the 5.65-MeV $1^{+}$. The solid curves denote the full calculation, including the nonresonant continuum. Note that the data in panel (a) represent the sum of the 2.19-MeV $3^{+}{}^6\mathrm{Li}$ resonance and the unresolved 2.15-MeV $1^{+}$ state of ${}^{10}\mathrm{B}$.

Figure 7

Comparison of the results of CDCC calculations with the 51-MeV ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ elastic scattering data of Ref. [1] (filled circles). The solid curve denotes the full calculation, including the nonresonant continuum, and the dotted curve the no-coupling result.

Figure 8

Comparison of the results of CDCC calculations with the 51-MeV ${}^{10}\mathrm{B}+{}^7\mathrm{Li}$ differential cross section data for (a) excitation of the ${}^7\mathrm{Li}$ 0.478-MeV $1/2^{-}$ bound excited state, (b) ${}^7\mathrm{Li}\to \alpha +t$ breakup via the 4.63-MeV $7/2^{-}L=3$ resonant state, and (c) ${}^7\mathrm{Li}\to \alpha +t$ breakup via the 6.68-MeV $5/2^{-}L=3$ resonant state. The solid curves denote the full calculation, including the nonresonant continuum, and the filled circles the data of Ref. [1].