Nuclear Astrophysics Experiments in Collaboration with Ruhr University

This Letter reports on two nuclear astrophysics experiments performed in collaboration with Ruhr University. In a ¹²C+¹²C fusion reaction, the ¹²C(¹²C,α)20Ne and ¹²C(¹²C,p)²³Na reactions were studied from E = 2.10 to 4.75 MeV using γ-ray spectroscopy. The deduced astrophysical S(E)* factor exhibited a new, strong resonance at E = 2.14 MeV, which lay at the high-energy tail of the Gamow peak. The resonance increased the reaction rate of the α-channel by a factor of five near T = 8×108 K. The electron screening in d(d,p)t was studied for a series of deuterated metal, insulator and semiconductor targets. Compared with the measurements performed with a gaseous D₂ target, a large effect was observed in most metals, while a comparatively small effect was found in the insulators and semiconductors. Subsequently the temperature dependence of the electron screening in the d(d,p)t reaction was studied for the deuterated metals Pt and Co. Enhanced electron screening decreased with increasing temperature. These data represent the first observations of the temperature dependence of a nuclear cross section.