Nuclear Seminar

Measuring reaction cross sections to understand the p process

Dr. Artemis Spyrou
NSCL, Michigan State University

Monday, November 24, 2008   4:00 p.m.   NSH 124
(Refreshments served prior to seminar in NSH 124)

Major effort was devoted in past decades for understanding of the different nucleosynthesis processes. There are still, however, many open questions that need to be resolved. One of the puzzles of nucleosynthesis is the production of a group of proton rich nuclei, the so called "p nuclei." The term p nuclei refers to 35 stable isotopes, in the mass region between Se (Z=34) and Hg (Z=80), which are 10-100 times less abundant than their more neutron rich neighbors. These rare nuclei are not produced by the two neutron induced (s- and r-) processes that can create all other nuclides beyond iron. Instead, a different mechanism was proposed for their synthesis called the "p process." To date, p-process nucleosynthesis models can reproduce most of the p-nuclei abundances within a factor of 3, but there are several cases where there are differences of up to more than one order of magnitude. These discrepancies can be attributed to the pure astrophysical input of the p-process modeling and/or to the nuclear physics contribution. This presentation will focus on the latter. The importance of capture reaction cross section measurements for p-process calculations will be stressed. Different experimental techniques will be described and recent results will be compared to theoretical calculations.