128 research outputs found
Investigation of alpha-induced reactions on 130Ba and 132Ba and their importance for the synthesis of heavy p nuclei
Captures of alpha particles on the proton-richest Barium isotope, 130Ba, have
been studied in order to provide cross section data for the modeling of the
astrophysical gamma process. The cross sections of the 130Ba(alpha,gamma)134Ce
and 130Ba(alpha,n)133Ce reactions have been measured with the activation
technique in the center-of mass energy range between 11.6 and 16 MeV, close
above the astrophysically relevant energies. As a side result, the cross
section of the 132Ba(alpha,n)135Ce reaction has also been measured. The results
are compared with the prediction of statistical model calculations, using
different input parameters such as alpha+nucleus optical potentials. It is
found that the (alpha,n) data can be reproduced employing the standard
alpha+nucleus optical potential widely used in astrophysical applications.
Assuming its validity also in the astrophysically relevant energy window, we
present new stellar reaction rates for 130Ba(alpha,gamma)134Ce and
132Ba(alpha,gamma)136Ce and their inverse reactions calculated with the SMARAGD
statistical model code. The highly increased 136Ce(gamma,alpha)132Ba rate
implies that the p nucleus 130Ba cannot directly receive contributions from the
Ce isotopic chain. Further measurements are required to better constrain this
result.Comment: Accepted for publication in Phys. Rev.
Experimental Be production cross section from the Li(p,n)Be reaction at E MeV
The Li(p,n)Be reaction is widely used as neutron source for neutron
induced reaction cross section measurements, and for Be radioactive source
production. There are two prominent structures in the excitation function, a
narrow resonance between MeV, and a broad peak, around
MeV. There are tension between the experimental data sets
both in the position and the width of this latter structure, as well as in the
absolute scale of the data. In the present work the Li(p,n)Be reaction
is investigated using the activation technique, with the aim of providing
comprehensive cross section data covering the second structure and connecting
prior literature data sets. The irradiations were performed with the Atomki
cyclotron accelerator with pairs of thin foil targets, thus with precisely
controlled reaction energy in the range of E MeV. After
the irradiations the activity of the samples was measured using a high-purity
germanium detector. The energy uncertainty of the new data points is much
smaller than in any of the previous works, while the cross section uncertainty
is comparable with the most precise literature data. A consistent data set was
obtained connecting the most recent and most precise literature data sets. With
the new data the absolute magnitude of the Li(p,n)Be reaction cross
section is constrained and became more precise.Comment: typos correcte
Experimental study of alpha-induced reactions on 64Zn for the astrophysical gamma-process
For the synthesis of the heavy, proton rich isotopes in the astrophysical
gamma-process the precise knowledge of alpha-induced cross sections is of high
importance. We have initiated a comprehensive study of the 64Zn+alpha system
involving the cross section measurement of different reaction channels as well
as the elastic scattering at low, astrophysically relevant energies. In this
paper the experimental technique and some preliminary results of the
64Zn(alpha,p)67Ga cross section measurement are presented.Comment: Accepted for publication in the proceedings of the Nuclear Physics in
Astrophysics V conference. To appear in Journal of Physics Conference Serie
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