Dipole strength distribution in 206Pb for the evaluation of the neutron capture cross section of 205Pb

The dipole strength distribution of 206Pb was investigated via a nuclear resonance fluorescence experiment using bremsstrahlung produced with an electron beam at a kinetic energy of 10.5 MeV at the linear accelerator ELBE. We identified 88 states resonantly excited at energies from 3.7 to 8.2 MeV. The analysis of the measured g-ray spectra includes the quasicontinuum of levels at high energy. Monte Carlo simulation of g-ray cascades were performed to obtain the intensities of inelastic transitions and branching ratios of the ground state transitions. The extracted photo-absorption cross section show enhanced dipole strength at the excitation energies around 5.5 and 7 MeV, which may related to a pygmy dipole resonance. The present (g,g) data combined with (g,n) data from the literature were used for confining input parameters of the statistical calculation code CCONE to derive the neutron capture cross section of the unstable 205Pb nucleus

Low energy measurement of the 14N(p,γ)15O total cross section at the LUNA underground facility

Deep underground in Gran Sasso National Laboratory (Italy), at the LUNA facility, the cross section of the N-14(p, gamma) O-15, the slowest process of the CNO cycle, has been measured at energies much lower than achieved before. Using a 400 kV accelerator, a windowless gas target and a 4 pi BGO summing detector, direct cross section data has been obtained down to 70 keV, reaching a value of 0.24 picobarn, corresponding to an S-factor of 1.74 +/- 0.14(stat) +/- 0.14(syst) keV barn. The Gamow peak has been covered by direct experimental data for several scenarios of stable and explosive hydrogen burning. The wy strength of the 259 keV resonance has been re-measured obtaining 12.8 +/- 0.3(stat) +/- 0.4(syst) meV. The stellar reaction rate has been calculated for temperatures 0.09 x 10(9) - 0.3 x 10(9) K. A complete description of the experiment is here presented, including the impact of the present data on nucleosynthesis in AGB stars