Asymptotic normalization coefficients from the (20)Ne((3)He, d)(21)Na reaction and astrophysical factor for (20)Ne(p,gamma)(21)Na

Journals published by the American Physical Society can be found at http://publish.aps.org/The (20)Ne(p,gamma)(21)Na reaction rate at stellar energies is dominated by capture to the ground state through the tail of a subthreshold resonance state at an excitation energy of 2425 keV in (21)Na. Both resonant and direct capture contribute to the reaction rate while direct captures to other bound states are negligible. The overall normalization of direct capture to the subthreshold state is determined by the asymptotic normalization coefficient (ANC). Simultaneously this ANC determines the proton partial width of the subthreshold resonance state. To determine the ANC, the (20)Ne((3)He,d)(21)Na proton transfer reaction has been measured, at an incident energy of 25.83 MeV. Angular distributions for proton transfer to the ground and first three excited states were measured, and ANCs were then extracted from comparison with distorted-wave Born approximation calculations. Using these ANCs, we calculated the astrophysical factor for (20)Ne(p,gamma)(21)Na. Our total astrophysical factor is S(0)=5900 +/- 1200 keV b. Our analysis confirms that only nonresonant and resonant captures through the subthreshold state are important

New astrophysical S factor for the (15)N(p,gamma)(16)O reaction via the asymptotic normalization coefficient (ANC) method

Journals published by the American Physical Society can be found at http://publish.aps.org/The (15)N(p,gamma)(16)O reaction provides a path from the CN cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor for this reaction is dominated by resonant capture through two strong J(pi) = 1(-) resonances at E(R) = 312 and 962 keV and direct capture to the ground state. Asymptotic normalization coefficients (ANCs) for the ground and seven excited states in (16)O were extracted from the comparison of experimental differential cross sections for the (15)N((3)He,d)(16)O reaction with distorted-wave Born approximation calculations. Using these ANCs and proton and alpha resonance widths determined from an R-matrix fit to the data from the (15)N(p,alpha)(12)C reaction, we carried out an R-matrix calculation to obtain the astrophysical factor for the (15)N(p,gamma)(16)O reaction. The results indicate that the direct capture contribution was previously overestimated. We find the astrophysical factor to be S(0) = 36.0 +/- 6.0 keV b, which is about a factor of 2 lower than the presently accepted value. We conclude that for every 2200 +/- 300 cycles of the main CN cycle one CN catalyst is lost due to this reaction

Asymptotic normalization coefficients for N-14 C-13+p from C-13(He-3,d)N-14

Journals published by the American Physical Society can be found at http://publish.aps.org/The C-13(He-3,d) N-14 proton transfer reaction has been measured at an incident energy of 26.3 MeV. Angular distributions for proton transfer to the ground state and excited states at 2.313 and 3.948 MeV in N-14 are analyzed within the framework of the modified DWBA. Asymptotic normalization coefficients (ANC's) defining the amplitude of the tails of the N-14 bound-state wave functions in the C-13+p channel are extracted that are in excellent agreement with values found previously with the C-13(N-14,C-13)N-14 reaction. We conclude that C-p1/2(2)=18.2(9) fm(-1) and C-p3/2(2) = 0.91(14) fm(-1) for the virtual decay N-14(g.s.) --> C-13+p. These are necessary for the analysis of the N-14(Be-7, B-8)C-13 and N-14( C-11, N-12) C-13 reactions to extract the ANC's far Be-7+p --> B-8 and C-11+p-->N-12, which determine the direct radiative capture cross sections Be-7(p,gamma)B-8 and C-11(p,gamma)N-12 at astrophysical energies

Publisher's Note: Asymptotic normalization coefficients for N-14+p -> O-15 and the astrophysical S factor for N-14(p,gamma)O-15 (vol 67, art no 065804, 2003)

Journals published by the American Physical Society can be found at http://publish.aps.org

Asymptotic normalization coefficients for 14N+p -> O-15 and the astrophysical S factor for N-14(p, gamma)O-15

Journals published by the American Physical Society can be found at http://publish.aps.org/The N-14(p,gamma)O-15 reaction, which controls energy production in the CNO cycle, has contributions from both resonance and direct captures to the ground and excited states. The overall normalization of the direct captures is defined by the corresponding asymptotic normalization coefficients (ANCs). Especially important is the ANC for the subthreshold state in O-15 at -0.504 keV since direct capture through this state dominates the reaction rate at stellar energies. In order to determine the ANCs for N-14+p-->O-15, the N-14(He-3,d)O-15 proton transfer reaction has been measured at an incident energy of 26.3 MeV. Angular distributions for proton transfer to the ground and five excited states were obtained. ANCs were then extracted from comparison to both distorted-wave Born approximation and coupled-channels Born approximation calculations. Using these ANCs, we calculated the astrophysical factor and reaction rates for N-14(p,gamma)O-15. Our analysis favors a low value for the astrophysical factor

Validity test of the Trojan Horse Method applied to the

The Trojan Horse Method (THM) was applied to the 3He+ 7Li interaction in order to investigate the quasi-free 7Li(p,α)4He reaction. The three-body experiment was performed at 33 MeV corresponding to a 7Li-p relative energy ranging from 50keV to 7MeV. The extracted 7Li(p,α)4He quasi-free cross-section was compared with the behavior of direct data, as well as with the result of a previous THM investigation on the 7Li(p,α)4He reaction off the neutron in 2H. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM