Narrow Results

Effects of tensor interactions in nucleus are discussed from the experimental view points. Two recent studies, one is the mixing of s- and p- waves in ¹¹Li halo and the other is the high momentum component in the nucleon wave function from a transfer reaction. Preliminary results of ¹⁶O(p,d)¹⁵O reaction show an abnormal relative enhancement of the transition to the positive parity state of ¹⁵O, which is not a hole state, consistent with contents of high momentum nucleon expected from the tensor interactions. The importance of the inclusion of tensor force, that can not be described in the mean field model, is discussed.

The reaction ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O was investigated through the direct $\alpha$-transfer reaction (⁷Li,t) at 28 and 34 MeV incident energies. We determined the reduced $\alpha$-widths of the sub-threshold 2${}^{+}$ and 1${}^{-}$ states of ${}^{16}$O from the DWBA analysis of the transfer reaction ${}^{12}$C(⁷Li,t)${}^{16}$O performed at two incident energies. The obtained result for the 2${}^{+}$ and 1${}^{-}$ sub-threshold resonances as introduced in the $R$-matrix fitting of radiative capture and elastic-scattering data to determine the E2 and E1 $S$-factor from 0.01MeV to 4.2MeV in the center-of-mass energy. After determining the astrophysic factor of ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O S(E) with Pierre Descouvement code, I determined numerically the new reaction rate of this reaction at a different stellar temperature (0.06 Gk-2 GK). The ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O reaction rate at T${}_9=0.2$ is [7.21${}_{-2.25}^{+2.15}$] × 10${}^{-15}$ cm³ s${}^{-1}$ mol${}^{-1}$. Some comparisons and discussions about our new ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O reaction rate are presented. The agreements of the reaction rate below T${}_9=2$ between our results and with those proposed by NACRE indicate that our results are reliable, and they could be included in the astrophysical reaction rate network.

In this paper, the $({}^3\mathrm{\text{He}},d)$ reactions are revisited, with the goal of obtaining spectroscopic factors (SF) for the transition to the ground state of some residual nuclei, applying the distorted wave Born approximation (DWBA). The double-folding São Paulo Potential (SPP) was used to derive the distorted wave function in the entrance and exit channels. The derived SF are compared with the results of extensive shell model calculations showing a rather good agreement.

Angular distribution of the ${}^{10}\mathrm{\text{B}}+{}^{12}\mathrm{\text{C}}$ elastic scattering was measured at $E_{\mathrm{\text{lab}}}({}^{10}\mathrm{\text{B}})=41.3$MeV. Experimental data showed a significant increase in differential cross-sections at backward angles. The optical model with phenomenological potentials reproduces well the experimental cross-sections in the region of the angles of the forward hemisphere, but is not able to explain the increase in cross-sections at large angles. The distorted wave Born approximation method was used to reproduce the experimental data at large angles $(>90^{\circ })$ by taking into consideration a deuteron transfer. Spectroscopic amplitude has been extracted for the configuration ${}^{12}$C${\to }^{10}$B + $d$ from the analysis.

The status of a new evaluation of astrophysical nuclear reaction rates, referred as NACRE- II, is reported. It includes 19 radiative capture and 15 transfer reactions on targets with mass numbers A < 16. This work is meant to supersede the NACRE compilation. Post-NACRE experimental data are taken into account. Extrapolations of the astrophysical S-factor to largely sub-Coulomb energies are based on the use of the potential model and of the distorted wave Born approximation (DWBA) for capture and transfer reactions, respectively. Adopted rates and their lower and upper limits are provided. Here, we illustrate with some results the general procedure followed in the construction of NACRE-II.

The two-proton decays of the low-lying states of ¹⁷Ne populated in the ¹H(¹⁸Ne,d)¹⁷Ne transfer reaction were studied. The two-proton width of the ¹⁷Ne first excited state at 1.288 MeV is of importance for two-proton radioactivity theory and nuclear astrophysics applications. Dedicated search of the two-proton emission off this state was performed leading to new upper limit Γ_2p/Γ_γ~1.3 × 10⁻⁴.