M. McCleskey

Study of excited states of {sup 31}S through beta-decay of {sup 31}Cl for nucleosynthesis in ONe novae

We have produced an intense and pure beam of 31Cl with the MARS Separator at the Texas A&M University and studied β‐decay of 31Cl by implanting the beam into a novel detector setup, capable of measuring β‐delayed protons and γ‐rays simultaneously. From our data, we have established decay scheme of 31Cl, found resonance energies with 1 keV precision, have measured its half‐life with under 1% accuracy, found its Isobar Analog State decay and by using the IMME obtained an improved mass excess for its ground state. In this contribution, a description of the used method along with selected preliminary experimental results are given and their relevance for novae nucleosynthesis discussed.

First observation of low-energy γ-ray enhancement in the rare-earth region

Here, the γ-ray strength function and level density in the quasi-continuum of 151,153Sm have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the γ strength down to unprecedentedly low γ energies of ≈ 500 keV. For the first time an enhanced low-energy γ-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low γ energies could have an impact of 2 3 orders of magnitude on the (n, γ) reaction rates for r-process nucleosynthesis.

Decay Spectroscopy for Nuclear Astrophysics: β‐delayed Proton Decay

Decay spectroscopy is one of the oldest indirect methods in nuclear astrophysics. We have developed at TAMU techniques to measure beta‐ and beta‐delayed proton decay of sd‐shell, proton‐rich nuclei. The short‐lived radioactive species are produced in‐flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. These allowed us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. At the same time we measure gamma‐rays up to 8 MeV with high resolution HPGe detectors. We have studied the decay of 23Al, 27P, 31Cl, all important for understanding explosive H‐burning in novae. The technique has shown a remarkable selectivity to beta‐delayed charged‐particle emission and works even at radioactive beam rates of a few pps. The states populated are resonances for the radiative proton capture reactions 22Na(p,γ)23Mg (crucial for the depletion of 22Na in novae), 26mAl(p,γ)27Si and 30P(p,γ)31S (bottleneck in novae and XRB b...

Precision half-life measurement of theβ+decay ofK37

The half-life of \tsups{37}K has been measured to be

Precision half-life measurement of the \boldmath

1.23651(94)~\mathrm{s}

\beta^+

, a value nearly an order of magnitude more precise than the best previously reported. The

decay of \tsups{37}K

\beta^+

The beta-delayed proton and gamma decay of 27P for nuclear astrophysics

decay of \tsups{37}K occurs mainly via a superallowed branch to the ground-state of its

Resonance Scattering to Study Exotic Nuclei at the Limits of Stability

T=1/2

Use of Neutron Transfer Reactions to Indirectly Determine Neutron Capture Cross Sections on Neutron‐Rich Nuclei

mirror, \tsups{37}Ar. This transition has been used recently, together with similar transitions from four other nuclei, as an alternative test of CVC and method for determining