Search

The 15O(α,γ)19Ne reaction is an important trigger reaction leading to the rapid proton (rp) capture process in X-ray bursts. The primary uncertainty in determining its astrophysical rate is the uncertain α branching ratios of levels near Ex = 4.1 MeV in 19Ne. These states have been populated in a study of the 20Ne(p, d)19Ne reaction, and α branching ratios are reported in this manuscript.

Many astrophysical events, such as novae and X-ray bursts, are powered by reactions with radioactive nuclei. Studying the properties of these nuclei in the laboratory can therefore further our understanding of these astrophysical explosions. The TwinSol separator at the University of Notre Dame has recently been used to produce intense (~106 pps) beams of 17F. In this article, some of the first measurements with these beams are discussed.

Clustering phenomena in 10Be and 18O were studied by means of resonance elastic scattering of α-particles on 6He and 14C. Excitation functions for α+6He and α+14C were measured and detailed R-matrix analyses of the excitation functions was performed. We compare the experimental results with the predictions of modern theoretical approaches and discuss properties of cluster rotational bands.

We discuss the identification and properties of the states that belong to the highly clustered rotational band in A=10 nuclei, 10Be, 10B(T=1) and 10C. The band is of interest because it may correspond to an exotic α:nn:α configuration.

Reactions involving radioactive nuclei play an important role in stellar explosions, but those reactions involving short-lived nuclei have only limited experimental information available due to currently limited beam intensities. Several facilities are aiming to provide greater access to these unstable isotopes at higher beam intensities, but more efficient and selective techniques and devices are needed to properly study these important reactions. The Array for Nuclear Astrophysics Studies with Exotic Nuclei (ANASEN), a charged particle detector designed by Louisiana State University (LSU) and Florida State University (FSU), was created for this purpose. ANASEN is used to study the reactions important in the αp- and rp- processes with proton-rich exotic nuclei, providing essentially complete solid angle coverage through an array of 40 silicon-strip detectors backed with CsI scintillators, covering an area of roughly 1300 cm2. ANASEN also includes an active gas target/detector in a position-sensitive annular gas proportional counter, which allows direct measurement of (α,p) reactions in inverse kinematics. The first in-beam measurements with a partial implementation of ANASEN were performed at the RESOLUT radioactive beam facility of FSU during the summer of 2011. They included stable beam experiments and measurements of the 17F(p,p)17F and 17F(p,α)14O reactions which are important to understanding the structure of 18Ne and the 14O(α,p)17F reaction rate. The performance of ANASEN and initial results from the 17F studies will be presented.

Isotopic abundances reflect both nuclear structure and environmental history. Observations are providing new evidence that is helping us to understand astrophysical phenomena, the chemical history of the Galaxy, and the origins of the diverse isotopic abundances found on earth. What we infer from observations, however, depends upon a robust understanding of the underlying nuclear physics. The difficulties involved in producing and studying short-lived isotopes are particularly problematic for understanding stellar explosions. While new facilities and experimental techniques have recently spurred significant progress in our understanding of the light, proton-rich nuclei that are important for understanding novae, studies of heavier exotic nuclei that are crucial for understanding more energetic explosions and the origins of the heavy elements are still quite challenging. We briefly survey recent progress in experimental nuclear physics that is important for understanding explosive nucleosynthesis and outline some of the major outstanding questions and the prospects for future advances.