Search

The fission probability of 232Pa was measured as a function of the excitation energy in order to search for hyperdeformed (HD) transmission resonances using the (d,pf) transfer reaction on a radioactive 231Pa target. The experiment was performed at the Tandem accelerator of the Maier-Leibnitz Laboratory (MLL) at Garching using the 231Pa (d,pf) reaction at a bombarding energy of Ed = 12MeV and with an energy resolution of ΔE = 5:5 keV. Two groups of transmission resonances have been observed at excitation energies of E* = 5:7 and 5.9MeV. The fine structure of the resonance group at E* = 5:7MeV could be interpreted as overlapping rotational bands with a rotational parameter characteristic to a HD nuclear shape (ħ²/2Θ = 2:05 keV). The fission barrier parameters of 232Pa have been determined by fitting TALYS nuclear reaction code calculations to the overall structure of the fission probability. [ABSTRACT FROM AUTHOR]

The direct and statistical neutron decay of the isoscalar giant dipole resonance has been studied in 90Zr, 116Sn, and 208Pb using the (α, α’ n) reaction at a bombarding energy of 200 MeV. The spectra of fast decay neutrons populating valence hole states of the Z, N − 1 nuclei were analyzed, and estimates for the branching ratios were determined. The observation of the nucleon-direct-decay channels helped to select giant-resonance strengths and suppress the underlying background and continuum, which led to an indication of the existence of a new mode with L = 2 character, presumably the overtone of the isoscalar giant quadrupole resonance. [ABSTRACT FROM AUTHOR]

The fission probability has been measured in the 231Pa(d, pf)232Pa and 231Pa(³He,df)232U reactions as a function of the excitation energy. In the fission probability of 232Pa new resonance groups were found and were interpreted as hyperdeformed rotational bands with a preliminary rotational parameter of ħ²/θ = 2.0-1.0+1.5 keV. However, in the case of 232U the fine structure of transmission resonances was not observed. [ABSTRACT FROM AUTHOR]

Abstract: A neutron spectrometer, the European Low-Energy Neutron Spectrometer (ELENS), has been constructed to study exotic nuclei in inverse-kinematics experiments. The spectrometer, which consists of plastic scintillator bars, can be operated in the neutron energy range of 100keV–10MeV. The neutron energy is determined using the time-of-flight technique, while the position of the neutron detection is deduced from the time-difference information from photomultipliers attached to both ends of each bar. A novel wrapping method has been developed for the plastic scintillators. The array has a larger than 25% detection efficiency for neutrons of approximately 500keV in kinetic energy and an angular resolution of less than 1°. Details of the design, construction and experimental tests of the spectrometer will be presented. [Copyright &y& Elsevier]

The photofission cross section of 238U was measured at sub-barrier energies as a function of the γ-ray energy using a monochromatic, high-brilliance, Compton-backscattered γ-ray beam. The experiment was performed at the High Intensity γ-ray Source (HIγS) facility at beam energies between Eγ = 4.7 MeV and 6.0 MeV and with ~3% energy resolution. Indications of transmission resonances have been observed at γ-ray beam energies of Eγ = 5.1 MeV and 5.6 MeV with moderate amplitudes. The triple-humped fission barrier parameters of 238U have been determined by fitting EMPIRE-3.1 nuclear reaction code calculations to the experimental photofission cross section. [ABSTRACT FROM AUTHOR]

Given the importance of Gamow-Teller (GT) transitions in nuclear structure and astrophysical nuclear processes, we have studied Tz = +3/2 → +1/2, GT transitions starting from the 47Ti nucleus in the (3He,t) charge-exchange reaction at 0° and at an intermediate incident energy of 140 MeV/nucleon. The experiments were carried out at the Research Center for Nuclear Physics (RCNP), Osaka, using the high-resolution facility with a high-dispersion beam line and the Grand-Raiden spectrometer. With an energy resolution of 20 keV, individual GT transitions were observed and GT strength was derived for each state populated up to an excitation energy (Ex) of 12.5 MeV. The GT strength was widely distributed from low excitation energy up to 12.5 MeV, where we had to stop the analysis because of the high level density. The distribution of the GT strengths was compared with the results of shell model calculations using the GXPF1 interaction. The calculations could reproduce the experimental GT distributions well. The GT transitions from the ground state of 47Ti and the M1 transitions from the isobaric analog state in 47V to the same low-lying states in 47V are analogous. It was found that the ratios of GT transition strengths to the ground state, the 0.088-MeV state, and the 0.146-MeV state are similar to the ratios of the strengths of the analogous M1 transitions from the isobaric analog state (IAS) to these states. The measured distribution of the GT strengths was also compared with those starting from the Tz = +3/2 nucleus 41K to the Tz = +1 /2 nucleus 41Ca. [ABSTRACT FROM AUTHOR]

Abstract: The full-energy peak efficiency calibration and the energy resolution measurements of the -ray detector are presented for -ray energies in the 700keV–17.6MeV range. Measurements were done using a combination of proton-capture nuclear reactions on , , , and for high-energy -rays, and radioactive sources such as and for the lowest energies. At high energies, two -rays in a cascade from proton resonance capture were employed using Al, , and targets. The obtained results were compared to the simulations performed using a GEANT4 code. [Copyright &y& Elsevier]