New Developments in Experimental Thermonuclear Reactions

Abstract

We review new developments regarding experimental thermonuclear reaction rates. First, it is pointed out that published experimental thermonuclear reaction rates have no rigorous statistical meaning. To overcome this problem, we have been working for the past 3 years on a new method of estimating experimental reaction rates by using a Monte Carlo method. Our new reaction rate evaluation for charged‐particle reactions on A = 14–40 target nuclei, which is based on this method, has just been completed. With these new reaction rates, many interesting aspects of nucleosynthesis and energy generation can be addressed that were previously not accessible. Second, as an example for a direct measurement, we discuss the recent study of the direct capture component in the 17O(p,γ)18F reaction at our LENA facility. The 17O+p reactions in classical novae are particularly important for the production of radioactive nuclei (mainly 18F), for the Galactic origin of 17O, and for oxygen isotopic ratios in nova presolar grains. Third, as an example for an indirect measurement, we discuss the recent 26Mg nuclear resonance fluorescence study at our HIγS facility. By measuring angular correlations using a linearly polarized γ‐ray beam, we determined the spins and parities of 5 levels near the α‐particle threshold in 26Mg. Thus we could substantially reduce the rate uncertainties for the 22Ne(α,n)25Mg neutron source. Our new reaction rates may have an important impact on the s‐process in both massive stars and in AGB stars.