The exotic beta-gamma-alpha decay mode of Na-20 has been directly observed for the first time in the Day-one experiment at the Beijing Radioactive Ion-beam Facility. The Na-20 source was produced by using a 100-MeV proton beam bombarding a stack of microporous MgO thick target and delivered as an intense mass separated beam after online ionization. A high-efficiency simultaneous measurement of beta, gamma, and alpha transitions enables the beta-delayed gamma-gamma and alpha-gamma coincidence spectroscopy. Three beta-gamma-alpha exotic decay sequences in Na-20 are discovered, which expands the rare decay modes observed in beta decay. Moreover, a beta-alpha-decay sequence to the 6130-keV 3(-) state of O-16 is observed, which is likely through the 12 367-keV 1(+) state in Ne-20. The experimentally deduced B(F) and B(GT) are compared to the shell-model calculation, the allowed beta transition strengths can be well accounted for by using sd shell-model space interactions.

Enriched targets of (SnO2)-Sn-116,118,120,122,124 were bombarded with proton and deuteron beams, and the angular distributions of (p, d) and (d, p) on tin isotopes were accurately measured using the high-precision Q3D magnetic spectrograph at the Beijing HI-13 tandem accelerator of the China Institute of Atomic Energy. Distorted-wave Born approximation calculations were performed to extract the neutron spectroscopic factors (SFs) using two different sets of systematic optical potential parameters for these neutron transfer reactions. The SFs of Sn116-125 were obtained and compared to previous values. Our results are consistent with the average of the previous data within the error range. It is worth noting that the reaction products corresponding to Sn-119(G.S.) and Sn-119(0.024)*, to Sn-123(G.S.) and Sn-123(0.025)*, and to Sn-125(G.S.) and Sn-125(0.028)* were first distinguished by the present experiment; therefore, our results of the low lying states of Sn-119,Sn-123,Sn-125 are more reliable. However, the first excited state of Sn-121 is only 0.006 MeV; we failed to identify the products that correspond to the ground state and the first excited state, and the extracted SFs of Sn-120(G.S) circle times n -> Sn-121(0.006.) and Sn-121(0.006) circle times n -> Sn-122(G.S) are not reliable. A simple linear formula was used to analyze the relationship of SFs with neutron separation energy S-n(N) and the even-A Sn pairing gap Delta(N), and SFs are found to be positively correlated to S-n(N) and Delta(N).

Mg-25(p, gamma) Al-26 is the most important reaction in the Mg-Al cycle in the hydrogen burning regions of stars. Its cross sections at stellar energies are essential to understand the issues of radioactive Al-26 in the galaxy and meteorites. The 57.7 keV resonance dominate the Mg-25(p, gamma) Al-26 astrophysical reaction rates at relative low temperature, but it is very difficult to measure its resonance strength directly, and the indirect measurement results deviate by a factor of about 2 by far. In this work, the angular distributions of Mg-25(Li-7, He-6) Al-26 leading to 6.364 MeV and eleven low-lying states in Al-26 have been measured by the Q3D magnetic spectrometer of the HI-13 tandem accelerator. The spectroscopic factors were derived and used to deduce the proton width and 57.7 keV resonance strength. The astrophysical Mg-25(p, gamma)Al-26 reaction rates at stellar energies have been updated by using the present result.

$^{25}\mathrm{Mg}(p,\ensuremath{\gamma})^{26}\mathrm{Al}$ is the most important reaction in the Mg-Al cycle in the hydrogen burning regions of stars. Its cross sections at stellar energies are essential to understand the issues of radioactive $^{26}\mathrm{Al}$ in the galaxy and meteorites. The 57.7 keV resonance dominate the $^{25}\mathrm{Mg}(p,\ensuremath{\gamma})^{26}\mathrm{Al}$ astrophysical reaction rates at relative low temperature, but it is very difficult to measure its resonance strength directly, and the indirect measurement results deviate by a factor of about 2 by far. In this work, the angular distributions of $^{25}\mathrm{Mg}(^{7}\mathrm{Li},^{6}\mathrm{He})^{26}\mathrm{Al}$ leading to 6.364 MeV and eleven low-lying states in $^{26}\mathrm{Al}$ have been measured by the Q3D magnetic spectrometer of the HI-13 tandem accelerator. The spectroscopic factors were derived and used to deduce the proton width and 57.7 keV resonance strength. The astrophysical $^{25}\mathrm{Mg}(p,\ensuremath{\gamma})^{26}\mathrm{Al}$ reaction rates at stellar energies have been updated by using the present result.

The 12C(α, γ)16O reaction plays a key role in the evolution of stars with masses of M > 0.55 M⊙. At the Gamow peak (Ec.m. = 300 ke V, T9 = 0.2), the cross section of the 12C(α, γ)16O reaction is so small (about 10−17 barn) that the direct measurement in ground laboratory is not feasible with the existing technology. Up to now, the cross sections at lower energies can only be extrapolated from the data at higher energies. However, two subthreshold resonances, locating at Ex = 7.117 MeV and Ex = 6.917 MeV, make this extrapolation more complicated. In this work the 6.917 MeV subthreshold resonance in the 12C(α, γ)16O reaction was investigated via the 12C(11B, 7Li)16O reaction. The experiment was performed using the Q3D magnetic spectrograph at HI-13 tandem accelerator. We measured the angular distribution of the 12C(11B, 7Li)16O transfer reaction leading to the 6.917 MeV state. Based on DWBA analysis, we derived the square of ANC of the 6.917 MeV level in 16O to be (2.45± 0.28) ×1010 fm−1, with which the reduced-α width can be computed. Finally, we calculated the astrophysical SE2 factor of the 6.917 MeV resonance to be 67.6 ± 7.7 ke V b.

The mechanism of the (d, p) reaction, which has been proven a powerful spectroscopic tool, is believed to be reasonably well understood. However, the 16O(d, p)17O reaction leading to the ground state in 17O seems to be a possible exception. It was found in the previous experiments that the 16O(d, p)17O angular distribution exhibits a rapid decline below the peak at the angle of 15 degrees. To date this abnormal behavior has not been reproduced by theoretical models. In this work we present a re-measurement of the 16O(d, p)Og.s.17 angular distribution by using a high-precision magnetic spectrograph. Our new angular distribution shows a slower decline than the previous data do. A comparative analysis with the distorted Born approximation (DWBA), the adiabatic distorted wave approximation (ADWA) and the continuum discretized coupled channels (CDCC) method suggests that the drop of the differential cross sections at the forward angles is due to the deuteron breakup coupling effects. In addition, we extracted the spectroscopic factor (SF) and the asymptotic normalization coefficient (ANC) for the 17O ground state.

We present the first experimental determination on the spectroscopic amplitudes (SAs) for the α-cluster in the B11 ground state via the Li7(Li6,d)11B reaction using a high-precision magnetic spectrograph. This is believed to have a strong effect on the studies of α-induced reactions which are crucial in nuclear astrophysics. It is found that the previous SAs of B11 from shell model calculations cause overestimations of up to 23% for the C12(α,γ)16O SE2(300) factor and up to 34% for the C13(α,n)16O S(190) factor with respect to the results from the present experimentally determined SAs. Due to the importance of these two reactions, for example the uncertainty in the C12(α,γ)16O cross section at Ec.m. = 300 keV is required to be better than 10% by stellar modeling, the new S-factors could result in a potential influence on the astrophysical network calculations.

Several zirconium isotopes are in the path of slow neutron capture (s) process, and the direct components of (n, gamma) reactions can be derived from their neutron spectroscopic factors. In the present work, the angular distributions of (C-12, C-13) and (C-13, C-12) reactions on targets Zr-90,Zr-92,Zr-94,Zr-96 were obtained using the high-precision Q3D magnetic spectrograph at the Beijing HI-13 tandem accelerator in China Institute of Atomic Energy. The distorted-wave Born approximation calculations were performed to extract the spectroscopic factors, using three different sets of Woods-Saxon potential parameters for these heavy-ion systems. The neutron spectroscopic factors for the ground state of Zr90-97 have been obtained and compared with other experimental data.

The ${}^{12}\mathrm{C}(\alpha,\gamma){}^{16}\mathrm{O}$ reaction plays a key role in the evolution of stars with masses of $M >$ 0.55 $M_\odot$. The cross-section of the ${}^{12}\mathrm{C}(\alpha,\gamma){}^{16}\mathrm{O}$ reaction within the Gamow window ($E_\textrm{c.m.}$ = 300 keV, $T_\textrm9$ = 0.2) is extremely small (about $10^{-17}$ barn), which makes the direct measurement in a ground-based laboratory with existing techniques unfeasible. Up until now, the cross-sections at lower energies can only be extrapolated from the data at higher energies. However, two subthreshold resonances, located at $E_x$ = 7.117 MeV and $E_x$ = 6.917 MeV, make this extrapolation more complicated. In this work, the 6.917 MeV subthreshold resonance in the ${}^{12}\mathrm{C}(\alpha,\gamma){}^{16}\mathrm{O}$ reaction was investigated via the ${}^{12}\mathrm{C}({}^{11}\mathrm{B},{}^{7}\mathrm{Li}){}^{16}\mathrm{O}$ reaction. The experiment was performed using the Q3D magnetic spectrograph at the HI-13 tandem accelerator. We measured the angular distribution of the ${}^{12}\mathrm{C}({}^{11}\mathrm{B},{}^{7}\mathrm{Li}){}^{16}\mathrm{O}$ transfer reaction leading to the 6.917 MeV state. Based on the FRDWBA analysis, we derived the asymptotic normalization coefficient (ANC) of the 6.917 MeV level in $^{16}$O to be (1.10 $\pm$ 0.29) $\times 10^{10}$ fm$^{-1}$, with which the reduced $\alpha$ width was computed to be $18.0\pm4.7$ keV at the channel radius of 6.5 fm. Finally, we calculated the astrophysical $S_{E2}(300)$ factor of the ground-state transitions to be 46.2 $\pm$ 7.7 keV b. The result for the astrophysical $S_{E2}(300)$ factor confirms the values obtained in various direct and indirect measurements and presents an independent examination of the most important data in nuclear astrophysics.