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New data for the reaction 11Be on 197Au at Elab = 31.9 MeV are presented. The angular distributions of the inelastically scattered 11Be and the 10Be fragments coming from the 11Be dissociation have been extracted and compared with semiclassical and coupled-channels calculations in an angular range ϑlab = 13°-46° for the detected Be fragment. [ABSTRACT FROM AUTHOR]

The 1S(p,γ)34Cl reaction is important for constraining predictions of certain isotopic abundances in oxygen-neon novae. Models currently predict as much as 150 times the solar abundance of 33S in oxygen-neon nova ejecta. This overproduction factor may, however, vary by orders of magnitude due to uncertainties in the 33S(p,γ)34Cl reaction rate at nova peak temperatures. Depending on this rate, 33S could potentially be used as a diagnostic tool for classifying certain types of presolar grains. Better knowledge of the 33S(p,γ)34Cl rate would also aid in interpreting nova observations over the S-Ca mass region and contribute to the firm establishment of the maximum endpoint of nova nucleosynthesis. Additionally, the total S elemental abundance which is affected by this reaction has been proposed as a thermometer to study the peak temperatures of novae. Previously, the 33S(p,γ)34Cl reaction rate had only been studied directly down to resonance energies of 432 keV. However, for nova peak temperatures of 0.2-0.4 GK there are 7 known states in 34Cl both below the 432 keV resonance and within the Gamow window that could play a dominant role. Direct measurements of the resonance strengths of these states were performed using the DRAGON recoil separator at TRIUMF. Additionally two new states within this energy region are reported. Several hydrodynamic simulations have been performed, using all available experimental information for the 33S(p,γ)34Cl rate, to explore the impact of the remaining uncertainty in this rate on nucleosynthesis in nova explosions. These calculations give a range of ~ 20-150 for the expected 33S overproduction factor, and a range of ~ 100-450 for the 32S/33S ratio expected in ONe novae. [ABSTRACT FROM AUTHOR]

We have used the 10B(³He, pacta) reaction at 4.9 MeV and the 11B(³He, dααα) reaction at 8.5 MeV to determine the energy, width, and decay mechanism of resonances in 12C above the triple-a threshold up to 21 MeV in excitation energy. Comparison with various models has allowed us to estimate the degree of clustering of the states studied. [ABSTRACT FROM AUTHOR]

Evidence has been found for a broad unbound state near 1 MeV excitation in 9B that is a candidate for the long-disputed A mirror of the unbound 1.68 MeV state in9Be. Reactions of6Li+6Li were studied with a 60 MeV beam incident on a 240 ug/cm2 6LiF target. The breakup fragments from the decay of the reaction products were detected in five Si-Si-Csl telescope detectors and the breakup particles were reconstructed using the technique of resonant particle spectroscopy. It is shown that contrary to a previous study, the 1/2+ is not populated in the reaction 6Li(6Li,i)9B, but that it is populated via the 6Li(66Li,rf)10 reaction. The sequential decays of 10B populated the channels 6Li(g.s.)+a, 6Li(2.186 MeV)+a, 8Be+d, and pnaa, with the latter including (9B+n or9Be+p) decay from 10B. Decays through 9B are identified and show the presence of the | state as a broad asymmetric peak around 0.8-1.0 MeV with Γ 1.5 MeV. [ABSTRACT FROM AUTHOR]

The 18Ne(α,p)21Na reaction provides one of the main HCNO-breakout routes into the rp process in x-ray bursts. The 18Ne(α,p0)21Na reaction cross section has been determined for the first time in the Gamow energy region for peak temperatures 7 ∼ 2 GK by measuring its time-reversal reaction 21Ne(p,α)18Ne in inverse kinematics. The astrophysical rate for ground-state to ground-state transitions was found to be a factor of 2 lower than Hauser-Feshbach theoretical predictions. Our reduced rate will affect the physical conditions under which breakout from the HCNO cycles occurs via the 18Ne(p,α)21Na reaction. [ABSTRACT FROM AUTHOR]

The current evaluation of the triple-α reaction rate assumes that the a decay of the 7.65 MeV, 0+ state in 12C, commonly known as the Hoyle state, proceeds sequentially via the ground state of 8Be. This assumption is challenged by the recent identification of two direct a-decay branches with a combined branching ratio of 17(5)%. If correct, this would imply a corresponding reduction in the triple-a reaction rate with important astrophysical consequences. We have used the 11B(3He, d) reaction to populate the Hoyle state and measured the decay to three a particles in complete kinematics. We find no evidence for direct α-decay branches, and hence our data do not support a revision of the triple-α reaction rate. We obtain an upper limit of 5 X 10-3 on the direct α decay of the Hoyle state at 95% C.L., which is 1 order of magnitude better than a previous upper limit. [ABSTRACT FROM AUTHOR]

The 17O(p,γ)18F reaction plays an important role in hydrogen-burning nucleosynthesis. Conflicting values for the low-energy behavior of its cross section exist in the literature. We present direct measurements of the astrophysical S factor of the 17O(p,γ)18F reaction at center-of-mass energies between 250 and 500 keV. These measurements were conducted in inverse kinematics at the DRAGON recoil separator. [ABSTRACT FROM AUTHOR]