The 22 Ne(p, γ) 23 Na reaction is part of the NeNa cycle of hydrogen burning.This cycle plays a key role in the nucleosynthesis of the elements between 20 Ne and 27 Al in red giant stars, asymptotic giant stars and classical nova explosions.The strengths of the resonances at proton energies above 400 keV are still affected by high uncertainty.In order to reduce this uncertainty, a precision study of the most intense resonances between 400 keV and 700 keV has been performed at the HZDR 3 MV Tandetron.The target, made of 22 Ne implanted in a 0.22 mm thick Ta backing, has been characterized using the 1222 keV and 458 keV resonances, well known in literature.Subsequently, the strengths of the resonances at 417, 611, and 632 keV were determined.Two HPGe detectors equipped with active anti-Compton shielding have been used.The uncertainty on the measured resonance strengths has been significantly lowered compared with previous values.

The $^{22}$Ne(p,$\gamma$)$^{23}$Na reaction is included in the neon-sodium cycle of hydrogen burning. A number of narrow resonances in the Gamow window dominates the thermonuclear reaction rate. Several resonance strengths are only poorly known. As a result, the $^{22}$Ne(p,$\gamma$)$^{23}$Na thermonuclear reaction rate is the most uncertain rate of the cycle. Here, a new experimental study of the strengths of the resonances at 436, 479, 639, 661, and 1279 keV proton beam energy is reported. The data have been obtained using a tantalum target implanted with $^{22}$Ne. The strengths $\omega\gamma$ of the resonances at 436, 639, and 661 keV have been determined with a relative approach, using the 479 and 1279 keV resonances for normalization. Subsequently, the ratio of resonance strengths of the 479 and 1279 keV resonances was determined, improving the precision of these two standards. The new data are consistent with, but more precise than, the literature with the exception of the resonance at 661 keV, which is found to be less intense by one order of magnitude. In addition, improved branching ratios have been determined for the gamma decay of the resonances at 436, 479, and 639 keV.

The strength of the E-p = 1.842 MeV resonance in the Ca-40(p,gamma) Sc-41 reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at E alpha = 4.5 MeV in the Ca-40(alpha,gamma) Ti-44 reaction. The present new value of omega gamma = ( 0.192 +/- 0.017) eV is 37% (equivalent to 3.5 sigma) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV Ca-40(p,gamma)Sc-41 and 4.5 MeV Ca-40(alpha,gamma) Ti-44 resonances has been determined to be 0.0229 +/- 0.0018. The newly corrected strength of the 1.842- MeV resonance can be used in the future as a normalization point for experiments with calcium targets.

The Ca-40(alpha, gamma)(44) Ti reaction is believed to be the main production channel for the radioactive nuclide Ti-44 in core-collapse supernovae. Radiation from decaying Ti-44 has been observed so far two supernova remnants, and precise knowledge of the Ti-44 production rate may help improve supernova models. The Ca-40(alpha, gamma)(44) Ti astrophysical reaction rate is determined by a number of narrow resonances. Here, the resonance triplet at E-alpha = 4497, 4510, and 4523 keV is studied both by activation, using an underground laboratory for the gamma counting, nuclear reactions. The strengths of the three resonances are determined to be omega gamma = (0.92 +/- 0.20), (6.2 +/- 0.5), and (1.32 +/- 0.24) eV, respectively, a factor of 2 more precise than before. The strengths of this resonance triplet may be used in future works as a point of reference. In addition, the present new data directly affect the astrophysical reaction rate at relatively high temperatures (above 3.5 GK).