Speaker
Andrew M. Rogers
(NSCL and Department of Physics & Astronomy and Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA)
Description
A complete understanding of the synthesis of the elements is one of the main outstanding questions
in nuclear astrophysics. A number of nucleosynthesis processes are known and to a reasonable
extent account for much of the observed solar abundances of nuclei. However, there are a number
of elements that can only be produced via processes involving proton rich nuclei. The rapid proton
capture or rp-process, is one such mechanism which occurs along the proton drip-line whereby fast
proton captures on seed nuclei followed by beta-decay allow for the production of elements possibly
as heavy as Te. Type I X-ray bursts are thought to be key sites for this process. To realistically
model the rp-process in these systems experimental data such as masses, lifetimes, and proton
capture rates along the proton drip-line are required. Such data are currently lacking for many of
these nuclei.
This work is supported by the National Science Foundation under Grant Nos. PHY-0606007 and PHY-9977707.
The 68Se waiting point is of particular interest, where a long beta-decay half-life coupled with
inhibited proton capture restricts the amount of material that is processed beyond mass 68 in
the rp-process. However, the reaction rate for the 2p-capture process 68Se+p -> 69Br+p -> 70Kr
depends exponentially on the Q-value and may bypass the waiting point. This Q-value is poorly
constrained. We have performed an experiment to measure Q-values of proton unbound states of
exotic nuclei at the National Superconducting Cyclotron Laboratory (NSCL) Coupled Cyclotron
Facility. The experiment was designed to reconstruct the decays of proton unbound nuclei, specifically 69Br, by detecting the decay protons using the MSU High Resolution Array (HiRA) in
coincidence with a heavy residue, e.g. 68Se, which is measured in the large acceptance S800 magnetic spectrograph. The first direct measurement of ground state proton emission from 69Br and general implications for the rp-process will be discussed.
Author
Andrew M. Rogers
(NSCL and Department of Physics & Astronomy and Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA)
Co-authors
A. Gade
(NSCL and Department of Physics & Astronomy, Michigan State University, East Lansing, MI 48824, USA)
D. Bazin
(National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA)
D. Galaviz
(Centro de Fisica Nuclear da Universidade de Lisboa, Lisboa, Portugal and NSCL and Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA)
D. Shapira
(Oakridge National Laboratory, Oak Ridge, TN 37831, USA)
F. Delaunay
(Laboratoire de Physique Corpusculaire, Caen, France)
J. Elson
(Department of Chemistry, Washington University, St. Louis, MO 63130, USA)
J. Lee
(NSCL and Department of Physics & Astronomy and Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA)
L.G. Sobotka
(Department of Chemistry, Washington University, St. Louis, MO 63130, USA)
M. Matos
(Oakridge National Laboratory, Oak Ridge, TN 37831, USA)
M. Mocko
(Los Alamos National Laboratory, Los Alamos, NM 87545, USA and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA)
M.A. Famiano
(Department of Physics, Western Michigan University, Kalamazoo, MI 49008,USA, and NSCL and Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA)
M.B. Tsang
(National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA)
M.S. Wallace
(Los Alamos National Laboratory, Los Alamos, NM 87545, USA)
R.J. Charity
(Department of Chemistry, Washington University, St. Louis, MO 63130, USA)
R.T. de Souza
(Indiana University Cyclotron Facility and Department of Chemistry, Bloomington, IN 47405, USA)
S. Hudan
(Indiana University Cyclotron Facility and Department of Chemistry, Bloomington, IN 47405, USA)
S. Lobostov
(FLNR/JINR, 141980 Dubna, Moscow region, Russian Federation)
S. Lukyanov
(FLNR/JINR, 141980 Dubna, Moscow region, Russian Federation)
W.G. Lynch
(NSCL and Department of Physics & Astronomy and Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA)