Speaker
Dr
Sotirios Harissopulos
(Institute of Nuclear Physics, NCSR "Demokritos")
Description
The origin in the cosmos of the so-called p nuclei is one of the most puzzling
tasks to be solved by any model of heavy-element nucleosynthesis. These nuclei are
by-passed by the s- and r-process pathways. To date, these nuclei have been
observed only in the solar system. Understanding the synthesis of these p-process
nuclei on the basis of astrophysical processes occurring outside the solar system,
like e.g. in exploding supernovae (SNII) or on He-accreting white dwarves with sub-
Chandrasekhar mass, which are both thought to be the most possible p-process sites,
will enable us not only to understand the nuclidic composition of the solar system
but also to further elucidate our fundamental picture of its creation.
Abundance calculations of the p nuclei make an extensive use of the nuclear
statistical model for the calculation of the rates of an extended reaction network.
Comparison with (p,gamma) and/or (n,gamma) cross section indicate that these rates
can be predicted within a factor of two. However, some very scarce (alpha,gamma)
data show that the reaction rates calculated using phenomenological alpha-particle
optical potentials can be wrong by a factor of ten or more. These uncertainties
might be reduced substantially by putting constraints on the alpha-particle optical
potentials that are so far poorly known at such low energies (E<12 MeV). In order
to achieve this goal, there exist different approaches, amongst which the
(alpha,gamma) measurements at sub-Coulomb energies in inverse kinematics using
state-of-the art detectors is the most transparent. The energies available at
ISOLDE (<3 MeV/u) in combination with the MINIBALL array and radioactive beams may
provide the most suitable experimental conditions to launch a nuclear astrophysics
program aiming at the study of the alpha potential. In this direction some first
ideas as well as first tests of the response of MINIBALL to capture events will be
presented.
Author
Dr
Sotirios Harissopulos
(Institute of Nuclear Physics, NCSR "Demokritos")
