Li Yun-Ju

Neutron spectroscopic factors of 7Li and astrophysical 6Li(n,g)7Li reaction rates

Angular distributions of the 7Li(6Li, 6Li)7Li elastic scattering and the 7Li(6Li, 7Lig.s.)6Li, 7Li(6Li, 7Li0.48)6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of 6Li + 7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation (DWBA) analysis, spectroscopic factors of 7Li = 6Li ⊗ n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in 7Li, respectively. Using the spectroscopic factors, the cross sections of the 6Li(n, γ0, 1)7Li direct neutron capture reactions and the astrophysical 6Li(n, γ)7Li reaction rates are derived.

Measurement of Angular Distribution for the 8Li(p, d)7Li Reaction

The 8Li(p, d)7Li reaction plays an important role in the inhomogeneous Big Bang nucleosynthesis and in the seed-nuclide production phase for the r-process. For the first time, its angular distribution at backward angles was measured in inverse kinematics at Ec.m. = 4.0 MeV by using an 8Li secondary beam. The result of measurement includes the contributions of 8Li(p, d0)7Li and 8Li(p, d1)7Li*. The 8Li(p, d0)7Li component is estimated to be 40%~58% in the mixture angular distribution by analysing the measured result.

Levels in 13N examined by 12C+p elastic resonance scattering with thick target*

The elastic resonance scattering of 12C+p has been studied in inverse kinematics via a novel thick target method at GIRAFFE facility of HI-13 tandem accelerator laboratory, Beijing. The recoil protons were measured by a ΔE-E counter telescope based on a large area double-sided silicon strip detector at laboratory angles around θ0 = 15°. The excitation function for 12C(p,p) elastic scattering has been obtained over a wide energy range of Ec.m.=0.31–3.45 MeV, which was explained quite well by the R-matrix calculation with known resonance parameters of the first three levels in 13N nucleus. Thus it is demonstrated that the present setup can be directly applied to the study of elastic resonance scattering with secondary radioactive beams.

Enhancement of β+-Decay Rate of 22Na in Metal Pd at Low Temperature

Temperature dependence of nuclear decays in metallic environments is a controversial issue. We measured the temperature dependence of the β+-decay half-life of22Na implanted into the metal host of palladium. It is found that the β+ -decay half-life of22Na in the metal Pd cooled to T = 15 K is shorter by 0.46(14)% than that at room temperature. The result is consistent in sign with, but clearly smaller than, the estimated one by the Debye model.

New Measurement of Proton Transfer Reactions and Elastic Scattering for 7Li + 13C at 34 MeV

The 13C(7Li, 6He)14N reaction is measured at E(7Li) = 34 MeV with the Q3D magnetic spectrometer of HI-13 tandem accelerator. Angular distributions at forward angles for proton transfer to the ground and the first excited states in 14N are obtained. In addition, angular distribution for 7Li + 13C elastic scattering is also measured. The optical potential parameters for the entrance and exit channels of the transfer reactions are derived by fitting the 7Li + 13C and 6Li + 14N elastic scattering experimental data, and their angular distributions are well reproduced by the distorted wave Born approximation calculations. A phase shift of about 2° between the calculations and the experiment data has been found in the earlier (7Li, 6He) study, whereas no such phase shift is observed in the present work.

Simulation and analysis of 13N+p elastic resonance scattering

The 13 N+p elastic resonance scattering has been studied at the secondary radioactive beam facility of CIAE in inverse kinematics via a thick-target method. The excitation function for the 13 N(p,p) scattering was obtained in the energy interval of Ecm 0.5|3.2 MeV with a 13 N secondary beam of (47:8 1:5) MeV. Careful analysis of the secondary beam components and extensive Monte-Carlo simulations enable the resolution of the experimental proton spectra. The resonance parameters for v e low-lying levels in 14 O were deduced by R- matrix tting calculations with MULTI7 and SAMMY-M6-BETA. The present results show general agreement with those from a recent similar work, and thus conrm the observation of a new 0 level at 5.7 MeV in 14 O with an improved width of 400(45) keV.

Determination of the Astrophysical S(E) Factors or Rates for Radiative Capture Reaction with One Nucleon Transfer Reaction

The radiative capture reaction plays an important role in nuclear astrophysics. We have indirectly measured the astrophysical S(E) factors for some proton capture reactions and reaction rates for several neutron capture reactions with one nucleon transfer reactions at HI-13 tandem accelerator in recent years. Some of them are compiled into IAEA EXFOR database and JINA REACLIB project, and used in the network calculations of Big Bang nucleosynthesis and type-I X-ray bursts.

Indirect Measurement of Astrophysical 13C(α, n)16O S-Factors

The 13C(α, n)16O reaction is believed to be the main neutron source reaction for the s-process in asymptotic giant branch (AGB) stars. The astrophysical S-factors of this reaction have been determined based on an evaluation of the α spectroscopic factor of the 1/2+ subthreshold state in 17O (Ex = 6.356 MeV) by using the 13C(11B, 7Li)17O α transfer reaction. Our result confirms that the 1/2+ subthreshold resonance is dominant for the 13C(α, n)16O reaction at low energies of astrophysical interest.

Determination of the Astrophysically Relevant 6 Li(n, γ) 7 Li Cross Sections from the 7 Li( 6 Li, 7 Li) 6 Li Elastic-Transfer Reaction

Angular distributions for the 7Li(6Li, 7Li)6Li elastic-transfer reaction have been measured with the Q3D magnetic spectrograph at the HI-13 tandem accelerator of Beijing, China. The neutron spectroscopic factors of 7Li are derived by comparing the calculated differential cross sections, which are obtained through the distorted-wave Born approximation (DWBA) calculation, to the experimental data. And these spectroscopic factors are then used to deduce the direct capture cross sections in 6Li(n, γ)7Li at energies of astrophysical relevance.

Angular distribution of 6He+p elastic scattering

The angular distribution of H-1(He-6,p)He-6 elastic scattering has been measured at E-c.m. = 4.3 MeV by using a thick-target inverse kinematic method. The experimental differential cross sections are reproduced by the distorted-wave Born approximation calculation utilizing the CH89 global optical potential parameter set. The real part of CH89 is reduced comparing with other potentials, which may be attributed to the couplings necessary for the weakly bound nuclei.The angular distribution of 1H(6He,p)6He elastic scattering has been measured at Ec.m. = 4.3 MeV by using a thick-target inverse kinematic method. The experimental differential cross sections are reproduced by the distorted-wave Born approximation calculation utilizing the CH89 global optical potential parameter set. The real part of CH89 is reduced comparing with other potentials, which may be attributed to the couplings necessary for the weakly bound nuclei.