Determination Of¹⁵N（n,γ）¹⁶N Astrophysical Reaction Rate And Proton Width Of¹⁶F Via Measurement Of （⁷Li,⁶Li） Reaction

Fluorine (19F) is a key element for nucleosynthetic studies sinceit is extremely sensitive to the physical conditions within stars. Fora long time, the Solar System was the only location within theGalaxy with known fluorine abundance. The astrophysical site ofthe production of fluorine has always been a puzzle as the Sun in themain sequence stage cannot produce flurine. The astrophysical siteto produce fluorine is suggested to be asymptotic giant branch (AGB)stars. In these stars, the production paths of19F are14N(α,γ)18F(β)18O(p,α)15N(α,γ)19F and14N(n,p)14C(α,γ)18O(p,α)15N(α,γ)19F.The15N(n,γ)16N reaction could affect the abundance of fluorine bycompeting with15N(α,γ)19F.The15N(n,γ)16N reaction rate depends directly on the neutronspectroscopic factors of the four low-lying states (the ground stateand the first three excited states) in16N. Shell model calculationsand two previous measurements of the (d,p) reaction yielded thespectroscopic factors with a discrepancy by a factor of~2.Therefore, it is worthwhile to perform a new measurement of theneutron spectroscopic factors for the four low-lying16N states viaan independent transfer reaction. The experiment was performed at the HI-13tandem acceleratorin Beijing. A7Li beam with an energy of44MeV was used to measurethe angular distributions of the15N(7Li,6Li)16N reaction populationthe ground state and the first three excited states at Ex=0.120,0.298and0.397MeV in16N. The angular distributions of the15N+7Lielastic scattering were also measured. In addition, a34.5MeV6Libeam was delivered for measurement of the15N+6Li elasticscattering. The reaction products were analyzed with a Q3Dmagnetic spectrograph. Based on distorted wave Bornapproximation analysis, the spectroscopic factors of the fourlow-lying16N levels were derived. Based on the new spectroscopicfactors we derived the15N(n,γ)16N reaction rate.The accuracy and precision of the spectroscopic factors areenhanced due to the first application of high-precision magneticspectrograph for resolving the closely spaced16N levels whichcannot be achieved in most recent measturments. The presentresult shed some light on the preexisting discrepancy of~2.The second goal of this thesis is the level widths of16F. All the16F levels are unbound by proton emission. To date the four low-lying16F levels have been experimentally identified with well establishedspin-parity values and excitation energies. However, there are stillconsiderable discrepancies for their level width. Therefore, it is stilldesirable to perform a new measurement of these level widths viaan independent approach.In this work, the proton widths of the four low-lying levels in16Fwere determined from the16N spectroscopic factors by chargesymmetry of mirror nuclei. The present work provides an important examination for the proton widths of16F via an independentexamination.