Astrophysical S factors of reactions with light nuclei
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trophysical S Factors of Reactions with Light Nuclei S. B. Dubovichenkoa and Yu. N. Uzikovb a
Fesenkov Astrophysical Institute NCSRT NSA RK, Almaty, Kazakhstan email: [email protected] Institute of Nuclear Physics NNC RK, Almaty, Kazakhstan b Joint Institute for Nuclear Research, Dubna, Moscow oblast, Russia email: [email protected]
Abstract—The twocluster model is a phenomenological semimicroscopic approach to the study of multi nucleon nuclear systems. In the framework of this model, interaction of nucleon clusters is described by the local twobody potential determined from the condition of description of data on cluster scattering and prop erties of their bound states. In this case the manybody character of the problem is taken into account approx imately in terms of Pauliallowed and Pauliforbidden states of the total nucleon system. Accounting for the dependence of cluster interaction potential on orbital Young schemes characterizing the properties of permu tation symmetry in the nucleon system is an important ingredient of the model. This approach is used for examination of photonuclear processes for p2H, p3H, p6Li, p12C and 4He12C, 3He4He, 3H4He, 2H4He sys tems and corresponding astrophysical S factors. It is demonstrated that this approach provides fairly good description of the data available in the lowenergy region, especially for systems with the number of nucleons A > 4 when errors for the phase shifts of cluster scattering extracted from experimental data are minimal. DOI: 10.1134/S1063779611020031
INTRODUCTION Experimental data on cross sections of nuclear reac tions are the main source of information on the cluster structure of the nucleus and the properties and mecha nisms of interaction between nuclei and their frag ments. Nuclear astrophysical experimental studies of reactions are complicated by the fact that the energy of matter interaction in stars is very low, from tenths to tens of kiloelectronvolts. In laboratory conditions it is prac tically impossible to perform direct measurements of cross sections of nuclear reactions necessary for astro physical calculations at such energies, with rare excep tions. Usually cross sections are measured at higher energies and then the obtained results are extrapolated to the energy range of interest for nuclear astrophysics [1]. However, as a rule, real measurements are related to a rather high energy (0.2–1 MeV) as compared to stellar energy; therefore, simple linear extrapolation of exper imental data to the astrophysical energy range is not always justified. Moreover, the interval of experimental errors in measured total radiative capture cross sections or astrophysical S factor at 3–300 keV in different sys tems reaches 100%, which highly depreciates results of such an extrapolation of experimental data. Therefore, in many cases only theoretical predic tions can fill a gap in experimental information on char acteristics of astrophysical fusion reactions. During recent years, due to essential progress in the chiral effec
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