Branching ratio Γα/Γγ of the 4.033 MeV 3/2+ state in 19Ne

The branching ratio Γα/Γγ of the 4.033 MeV 3/2+ state in 19Ne plays a crucial role in the breakout from the hot CNO cycle into the rapid proton capture process. This ratio has been studied by making use of the advantages of inverse kinematics. The state was populated via the 3He(20Ne,α) 19Ne* reaction and its decay via γ or α emission was measured by detecting the heavy reaction products (19Ne or 15O) in coincidence in a magnetic spectrograph. An upper limit Γα/Γγ≤6×10-4 has been obtained. With these results, the astrophysical reaction rate for the 15O (α, γ) 19Ne reaction has been calculated. Its influence on the breakout at various astrophysical sites, novas, x-ray bursts, and supermassive stars, is discussed

First evidence of fusion hindrance for a small Q-value system

The excitation function for the fusion-evaporation reaction 28Si + 64Ni has been measured down to a cross section of 25 nb. This is the first observation of fusion hindrance at extreme sub-barrier energies for a system with a small, negative Q-value (- 1.78 MeV). This result is further proof that heavy-ion fusion hindrance, reported earlier only for systems with large, negative Q-values, is a general phenomenon. The measured behavior can be reproduced by coupled-channels calculations with a modified ion-ion potential incorporating the effects of nuclear incompressibility

Forensic analysis of tempered sheet glass by particle induced X-ray emission (PIXE)

The elemental concentrations of five trace elements in tempered sheet glass fragments were determined using particle-induced X-ray emission (PIXE) spectrometry. The trace element concentrations for calcium, iron, manganese, strontium, and titanium are compared to those obtained by inductively-coupled plasma-atomic emission spectrometry (ICP-AES) following complete digestion by hydrofluoric acid. For these five elements, the absolute concentrations obtained by both methods are shown to agree well over a wide range of concentrations. The limits of detection for trace elements are typically lower for the ICP-AES method. However, we show that the concentrations of these five elements can be accurately measured by the PIXE method. Since PIXE is an entirely non-destructive method, there exists a niche for this technique to be used as a complement to the more sensitive ICP-AES technique in the forensic analysis of sheet glass

Structure of He7 by proton removal from Li8 with the (d,3He) reaction

We report on a study of the structure of the unbound nucleus He7 utilizing the proton-removal reaction 2H(8Li,3He)7He. Combining the present results with those of our prior measurements of the neutron-adding reaction 2H(6He,p)7He, a consistent picture emerges for the low-lying excitations in He7. Specifically, the negative-parity sequence of resonances, in order of excitation energies, is consistent with 3/2-,1/2-, and 5/2-. The stable-beam reactions 2H(7Li,t)6Li and 2H(7Li,3He)6He were also measured. The results are compared with the predictions of nuclear structure models, including those of ab initio quantum Monte Carlo calculations. © 2008 The American Physical Society

The Structure of \u3csup\u3e7\u3c/sup\u3e He

We have studied the properties of the unbound isotope of helium 7He, using the 2H(8Li,3He)7He reaction. When combined with prior measurements of the 2H(6He,p)7He reaction the data present a consistent picture for the low-lying excited states of 7He, specifically the negative parity sequence 3/2- (ground state) 1/2- (first-excited) and 5/2- (second-excited). The shapes but not the absolute magnitudes of the angular distributions are reproduced by ab-initio theory coupled with a DWBA reaction framework

Structure of He-7 by proton removal from Li-8 with the (d,He-3) reaction

We report on a study of the structure of the unbound nucleus He-7 utilizing the proton-removal reaction H-2(Li-8,He-3)He-7. Combining the present results with those of our prior measurements of the neutron-adding reaction H-2(He-6,p)He-7, a consistent picture emerges for the low-lying excitations in He-7. Specifically, the negative-parity sequence of resonances, in order of excitation energies, is consistent with 3/2(-),1/2(-), and 5/2(-). The stable-beam reactions H-2(Li-7,t)Li-6 and H-2(Li-7,He-3)He-6 were also measured. The results are compared with the predictions of nuclear structure models, including those of ab initio quantum Monte Carlo calculations

Nucleon transfer reactions with exotic beams at ATLAS

We present some recent results from studies of light nuclei using exotic beams from ATLAS at Argonne National Laboratory. Light nuclei far from stability provide ideal testing grounds for modern theoretical methods, and may provide information about astrophysical environments. We focus on the nuclei Li-9 and He-7, populated with the (d,p) and (d,He-3) reactions

Detection, half-life and production of p-process nuclide 146Sm

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