Jean Vervier

Louvain-Edinburgh Detector Array (LEDA): a silicon detector array for use with radioactive nuclear beams

We discuss the design and implementation of the Louvain-Edinburgh Detector Array: a charged particle detector array composed of silicon-strip detectors which is used for the study of nuclear astrophysics and nuclear physics using radioactive nuclear beams at the Louvain-1a-Neuve radioactive nuclear beam facility

A Direct Measurement of the F-18(p,Alpha)o-15 Reaction

The cross section for the F-18(p,alpha) O-15 reaction has been obtained in reverse kinematics (F-18 beam on CH2 target) between 550 and 740 keV above threshold, i.e. in a region of astrophysical interest. The reaction yield is dominated by a wide resonant state whose spin, parity, total width and partial widths were deduced from the analysis of the alpha-particle and elastic proton data.

Long range absorption in the scattering of 6He on 208Pb and 197Au at 27 MeV

Quasi-elastic scattering of 6He at E_lab=27 MeV from 197Au has been measured in the angular range of 6-72 degrees in the laboratory system employing LEDA and LAMP detection systems. These data, along with previously analysed data of 6He + 208Pb at the same energy, are analyzed using Optical Model calculations. The role of Coulomb dipole polarizability has been investigated. Large imaginary diffuseness parameters are required to fit the data. This result is an evidence for long range absorption mechanisms in 6He induced reactions. Comment: 10 pages, 10 figures, minor corrections. To appear in Nucl. Phys. A

Twin backbending in 156Dy

Abstract The ground-state and β-bands in 156 Dy have been definitely established up to 20 + using the (α, 8n) and (p, 4n) reactions. They cross at 16 + . Two backbendings were observed and attributed to the crossing of a third band with these two bands.

Two proton emission induced via a resonance reaction

A radioactive beam of N-13 ions was used to bombard a (CH2)(n) target in order to populate a narrow resonance at 7.77 MeV in O-14. A weak two proton decay branch was observed with a width of 125 +/- 20 eV which occurs predominantly by a sequential mechanism. A limit for He-2 emission of Gamma(2He) < 6 eV is compared with calculations.

The 93Nb(d, p)94Nb reaction and the low-lying states of 94Nb

Abstract A large number of states up to approximately 3.3 MeV have been observed in the reaction 93Nb(d, p)94Nb utilizing magnetic analysis of the protons. A quintuplet of levels near the ground state is identified as the low-lying part of the configuration (π g 9 2 )(ν d 5 2 ) 3 . an interpretation of the data is made utilizing the recently established (p, n) residual interaction in 92Nb to calculate the low-lying levels of 94Nb. The energies of the observed levels and the intensities of the corresponding proton groups are well reproduced by the calculations.

Section efficace de capture radiative pour des neutrons d'une source Sb-Be

Resume Radiative capture cross sections of 7 isotopes for 25-keV Sb-Be photoneutrons have been measured by comparison with the corresponding thermal neutron cross sections; the agreement with previous measurements is satisfactory.

SPINOR SYMMETRY AND SUPERSYMMETRY IN THE Ru, Rh, Pd AND Ag ISOTOPES

Abstract Experimental data on excitation energies and B(E2) values in the even-even Ru and Pd, and odd-A Rh and Ag isotopes suggest the existence of a Spin(3) spinor symmetry and a U ( 6 2 ) supersymmetry in these nuclei, wherein the even-even isotopes are described by the SU(5) limit of the interacting boson model and the odd proton of the odd-A isotopes is in a j = 1 2 orbit.

Multipolarities of prompt transitions in 156Dy and spin-parities of the upper band levels

Abstract The prompt γ-ray and conversion-electron spectra following the 159 Tb(p, 4n) 156 Dy and 156 Gd(α, 4n) 156 Dy reactions have been measured with, respectively, a Ge(Li)-NaI(Tl) Compton suppression device and a mini-orange spectrometer. On the basis of the deduced multipolarities, earlier spin-parity assignments for levels in 156 Dy have been confirmed. Furthermore, the recently reported upper band levels could be divided into a negative-parity band up to 11 − or maybe 13 − , and a positive-parity band with tentative K = 0 character and spins 4 + , 6 + , 8 + , 10 + and maybe 2 + . The negative-parity band is described as an aligned-octupole band; the positive-parity band may possibly represent the low-spin extension of the superband responsible for backbending in the β- and ground-state bands in this nucleus.

Dynamical supersymmetry in 196Pt and 197Au

Abstract The excitation energies, reduced E2 transition probabilities and spectroscopic factors in the ( 3 He, d ) reaction for the levels with positive parity in 197 Au up to about 1 MeV, together with the corresponding data for 196 Pt , are shown to be in overall agreement with the predictions of a dynamical supersymmetry scheme recently proposed for nuclei in this mass region.