Abstract
In experimental nuclear astrophysics it is common knowledge that reaction cross sections must be measured in the astrophysically relevant, low energy ranges or at least as close to them as possible. In most of the cases, however, it is impossible to reach such low energies. The reactions must therefore be studied at higher energies and the cross sections must be extrapolated to lower ones. In this paper the importance of cross section measurements in wide energy ranges are emphasized and a few examples are shown from the areas of hydrogen burning processes and heavy element nucleosynthesis.
Highlights
For the modeling of astrophysical phenomena, including stellar evolution itself and various nucleosynthetic processes, the rates of nuclear reactions participating in a given process must be known at the corresponding stellar temperatures
The reaction rates can be obtained from the cross sections in the relevant energy ranges, i.e. in their Gamow windows
In most of the astrophysical processes the temperatures are so low that the Gamow windows are located way below the Coulomb barrier and the cross sections are tiny
Summary
For the modeling of astrophysical phenomena, including stellar evolution itself and various nucleosynthetic processes, the rates of nuclear reactions participating in a given process must be known at the corresponding stellar temperatures. In various hydrogen burning processes low mass nuclei are involved which are characterized by low level densities In these cases the R-matrix approach is - among others - a standard procedure for obtaining low energy cross sections. 2. The activation method In this paper a few examples will be shown briefly where experimental data at energies much higher than the Gamow windows are useful and were obtained recently at Atomki. All these reactions were studied using the activation method, i.e. the cross sections were determined by the decay measurement of the created radioactive isotopes. The activation method provides directly the astrophysically relevant total cross section and the results are largely independent from the data obtained from in-beam experiments.
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