Constraining the astrophysical origin of the p-nuclei through nuclear physics and meteoritic data

Abstract

Abstract. A small number of naturally occurring, proton-rich nuclides (the p-nuclei) cannot be made in the s-and r-process. Their origin is not well understood. Massive stars can produce p-nuclei through photodisintegration of pre-existing intermediate and heavy nuclei. This so-called γ-process requires high stellar plasma temperatures and occurs mainly in explosive O/Ne burning during a core-collapse supernova. Although the γ-process in massive stars has been successful in producing a large range of p-nuclei, significant deficiences remain. An increasing number of processes and sites has been studied in recent years in search of viable alternatives replacing or supplementing the massive star models. A large number of unstable nuclei, however, with only theoretically predicted reaction rates are included in the reaction network and thus the nuclear input may also bear considerable uncertainties. The current status of astrophysical models, nuclear input, and observational constraints is reviewed. After an overview of currently discussed models, the focus is on the possibility to better constrain those models through different means. Meteoritic data not only provide the actual isotopic abundances of the p-nuclei but can also put constraints on the possible contribution of proton-rich nucleosynthesis. The main part of the review focusses on the nuclear uncertainties involved in the determination of the astrophysical reaction rates required for the extended reaction networks used in nucleosynthesis studies. Experimental approaches are discussed together with their necessary connection to theory, which is especially pronounced for reactions with intermediate and heavy nuclei in explosive nuclear burning, even close to stability.

High precision113In(α,α)113In elastic scattering at energies near the Coulomb barrie

“…About 99% of the isotopes heavier than iron are synthesized via neutron capture reactions in the so-called s and r processes [16]. However, on the proton-rich side of the valley of stability there are about 35 nuclei separated from the path of the neutron capture processes.…”

“…However, on the proton-rich side of the valley of stability there are about 35 nuclei separated from the path of the neutron capture processes. These mostly even-even isotopes between 74 Se and 196 Hg are the so-called p nuclei [16]. It is generally accepted that the main stellar mechanism synthesizing the p nuclei-the so-called γ process-involves mainly photodisintegrations, dominantly (γ, n) reactions on preexisting more neutron-rich s and r seed nuclei.…”

Production Uncertainties of p-Nuclei in the γ-Process in Massive Stars Using a Monte Carlo Approach

“…The majority of p-nuclei are made in photodisintegration processes in outer shells of massive stars in the course of the final supernova explosion, the γ-process. Whether this is sufficient to explain the terrestrial p-abundances remains an open question, as this is the result of a superposition of nuclei produced in various sources over time [1,2].…”

Proton capture cross section ofGe72and astrophysical implications

“…Reaction rates constitute one of the main nuclear inputs required by astrophysical calculations in modeling the processes responsible for the synthesis of all the elements [1][2][3][4]. The main processes believed to produce most of the heavier nuclei are the rapid- [2] and slow- [3] neutron-induced capture processes.…”

“…The main processes believed to produce most of the heavier nuclei are the rapid- [2] and slow- [3] neutron-induced capture processes. A third production mechanism, called the p-process, exists which creates proton-rich nuclei in the mass region between Z = 28 and Z = 80 [1,4]. There are 35 stable isotopes called the pnuclei which are produced only by the p-process.…”