106,108Cd(p,γ)107,109In cross sections for the astrophysical p-process

Complete text of publication follows. As a continuation of a systematic study of reactions relevant to the astrophysical p-process, the capture as well as the elastic scattering cross sections of the 106Cd nucleus have been recently measured at ATOMKI. In order to give a complete description of 106Cd nucleus from the astrophysical p-process point of view, it is also necessary to measure the proton capture cross section of this isotope in the astrophysically relevant energy range and to compare the result with the predictions of statistical model calculations which are used in p-process modeling. The proton capture cross section measurement has been carried out using the activation technique. In contrary to the case of the (α,γ) experiment, the proton capture of the other p-isotope of cadmium (108Cd) also leads to a radioactive reaction product. Therefore it was possible to measure the (p,γ) cross section for both p-isotopes of cadmium: 106Cd and 108Cd. The experiments have been carried out at the Van de Graaff and cyclotron accelerators of ATOMKI. The lower part of the investigated energy region between 2.4 and 3.6MeV was measured at the Van de Graaf while the upper part between 3.6 and 4.8MeV at the cyclotron. In order to find any possible systematic difference between the results obtained at the two accelerators, the Ep = 3.6MeV point has been measured with both accelerators, and perfect agreement was found. Highly enriched 106Cd as well as natural Cd evaporated onto thin Al backing was used for targets. The 108Cd content in the enriched 106Cd was still higher than the natural abundance thus the 108Cd(p,γ) could be measured also with the enriched targets. In the lower part of the measured energy range, where the cross section of the studied reactions is small, the enriched targets were used in order to avoid the disturbing background coming from proton induced reactions on heavier Cd isotopes. The γ-radiation from the decay of the produced 107In and 109In isotopes was measured with calibrated HPGe detector. For the analysis the recently measured precise half-life of 109In has been used. The resulting cross sections have been compared with the predictions of the statistical model calculations using the NON-SMOKER code. For both measured reactions there is a good agreement between the measurements and the calculations. Fig. 1. shows the results in the form of astrophysical S-factor. The measured points obtained with enriched and natural targets are shown with different symbols. The results of the model calculations are also shown. The final analysis of the results is still in progress where the dependence of the model calculations on di rent input parameters will also be studied. (author)