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In this paper we show how effective parameters such as effective binding energies can be defined for a proton in the combined nuclear-Coulomb potential, including also the target potential, in the case in which the proton is bound in a nucleus which is partner of a nuclear reaction. Using such effective parameters the proton behaves similarly to a neutron. In this way some unexpected results obtained from dynamical calculations for reactions initiated by very weakly bound proton halo nuclei can be interpreted. Namely the fact that stripping dominates the nuclear breakup cross section which in turn dominates over the Coulomb breakup even when the target is heavy at medium to high incident energies. Our interpretation helps also clarifying why the existence and characteristics of a proton halo extracted from different types of data have sometimes appeared contradictory. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Two-proton radioactivity was predicted more than 40 years ago. According to recent theoretical predictions, proton drip-line nuclei in the A=40–55 region were identified as the most promising candidates. The recent observation of two-proton radioactivity of 45Fe confirmed these predictions nicely. In the present paper, we will summarize experimental results for the decay of 45Fe, which include data from the 2002 discovery of this radcioactivity, but also new data. In addition, we will report on the first observation of 54Zn and its decay by two-proton radioactivity, the second case of this new decay mode. Finally, we will discuss tentative evidence for a small two-proton radioactivity branch for 48Ni. These experimental results are confronted to modern theories which succeed in describing reasonably well this decay mode. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Understanding the phenomenon of one-proton emission is crucial for addressing the question of the location of the limits of observable nuclei. Much of the current understanding of this radioactive decay process has been developed and refined through measurements of proton emitters above Z = 50, where ∼30 proton-emitting nuclei have already been discovered and studied. However, despite the great experimental and theoretical efforts over recent years, some important questions remain unanswered. Possibilities for future experiments to tackle some of these issues are considered. [ABSTRACT FROM AUTHOR]

Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Therefore, relatively small differences in the total proton stopping power given, for example, by the different models provided by GEANT4 can lead to significant disagreements in the final proton energy spectra when integrated along lengthy proton trajectories. This work presents proton energy spectra obtained by GEANT4.8.2 simulations using ICRU49, Ziegler1985 and Ziegler2000 models for 19.68 MeV protons passing through a number of Al absorbers with various thicknesses. The spectra were compared with the experimental data, with TRIM/SRIM2008 and MCNPX2.4.0 simulations, and with the Payne analytical solution for the transport equation in the Fokker-Plank approximation. It is shown that the MCNPX simulations reasonably reproduce well all experimental spectra. For the relatively thin targets all the methods give practically identical results but this is not the same for the thick absorbers. It should be noted that all the spectra were measured at the proton energies significantly above 2 MeV, i.e., in the so-called “Bethe-Bloch region”. Therefore the observed disagreements in GEANT4 results, simulated with different models, are somewhat unexpected. Further studies are necessary for better understanding and definitive conclusions. [ABSTRACT FROM AUTHOR]

The astrophysical s-process is responsible for the synthesis of many of the nuclei heavier than iron through a series of low-energy (n,γ) reactions and β-decays. For nuclei for which the neutron capture and β-decay rates are comparable, the branching is crucial for tests of s-process models. Direct measurements of (n,γ) cross sections for these nuclei are extremely challenging due to the inherent difficulties associated with radioactive targets and the low intensity of available neutron beams. The surrogate reaction technique can be used to circumvent these difficulties by creating the same compound nucleus through light-ion reactions on a stable target. The cross section can be determined by combining optical model calculations for the formation of the compound nucleus with the measured exit channel probability for γ-ray emission. We have collected data to determine the low-energy (n,γ) cross section for the unstable nucleus 153Gd by bombarding a stable 154Gd target with protons from the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory to create the desired 154Gd* compound nucleus. The STARS/LiBerACE silicon and clover germanium detector arrays were used to detect γ-rays in coincidence with the scattered protons. Additional cross section measurements using 156Gd and 158Gd targets will be compared to direct measurements of the (n,γ) cross sections for 155Gd and 157Gd. The current status of the analysis is summarized. [ABSTRACT FROM AUTHOR]