Etude expérimentale de l'isométrie des noyaux atomiques Hf178, Sb122 et Sb124

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Timing properties of a 'Lege'-type (low energy germanium) detector

Time properties of a "Lege"-type detector are investigated using coincidence- and risetime measurements and calculating the potential distribution inside the crystal. It is shown that γ-rays stopped in the noncentral part of the Ge crystal give rise to long risetimes and consequently to 'Leading-Edge' timing in the constant fraction module. © 1987.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Collective and shell-model excitations in 9745Rh52

97Rh has been studied by deexcitation of the compound nucleus formed through the reactions 96Ru(3He,pn) at 20 MeV and 96Ru(2H,n) at 9 MeV. Direct γ-spectra, multidimensional γγ coincidences and angular distribution measurements lead to a proposed level scheme. These levels are compared to calculations based on the interacting boson-fermion approximation IBFA model in which the odd particle moves in the 1g 9 2 orbital. Evidence for the observation of shell-model states outside the sd boson configuration space in 97Rh is obtained. © 1983.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

High-spin levels in the 199Pb and 200Pb isotopes

The de-excitation of the 200Pb and 199Pb isotopes, produced through the 186W(18O,4n, 5n) reactions, is investigated using γ-ray and conversion electron spectroscopy. The conversion coefficients are measured and the multipolarities deduced for a great number of transitions. The e-γ- and γγ-coincidences and the half-life measurements lead to several new levels in both level schemes; the 200Pb one is extended up to nearly 7 MeV, where an isomer is found. The experimental results are compared to those of microscopic calculations, performed in a two or three quasi-particle approximation, using a surface delta interaction with a reduced pairing component. © 1988.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

[Formula Presented] isotope properties as a cosmothermometer

The [Formula Presented] properties as a cosmochronometer and a cosmothermometer are studied, combining Coulomb excitation with the recoil method. The results confirm that this isotope should be dismissed as a reliable cosmochronometer. On the other hand, this nucleus synthesis takes place, in all probability, at temperatures between [Formula Presented] and [Formula Presented] The assignment of the levels reached leads to some difficulties as to their reduced transition probabilities. © 2000 The American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Excited states of97Pd

The97Pd nucleus has been studied from the reaction96Ru(3He, 2 n)97Pd. From in and out beam direct γ-spectra and γ-γ coincidences a partial level scheme is proposed. The observed high spin states can be explained by the coupling of the even proton core with the d5/2 51st neutron. © 1982 Springer-Verlag.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Spectroscopic study of short lived, high spin isomers through the recoil method

The γ and conversion electron de-excitation spectra of nuclei, produced through (HI, χn) reactions, are spoiled by various phenomena, most of them related to the reaction itself. When, in the isotopes studied, one or several isomers are present, the half-life of the higher energy one being about 15 ns or more, then the compound nucleus recoil method can provide much cleaner spectra. This method is extensively described and discussed here, together with others, more briefly treated, also meant to reduce the unwanted effects; these techniques may be used either separately or combined, depending on the experiments performed. Examples of the results obtained are shown to illustrate the substantial improvements reached. © 1988.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

De-excitation of high spin isomers in the 191Pb isotope

The 191Pb isotope, produced through different A(b,xn) 191Pb reactions, where b stands for nuclei such as 16O, 20Ne, and 31P, is studied. The half-life of some excited levels being greater than 10 ns, the recoil catcher method is suitable to look into the de-excitation γ ray and conversion electron spectra of these states. The conversion coefficients are deduced and e--γ and γ-γ coincidence measurements lead to the part of the level scheme de-exciting these isomers. This level scheme is compared to theoretical predictions obtained through a microscopic calculation in a three quasi-particle approximation, using a surface delta interaction with a reduced pairing component. The conclusions are very similar to those previously obtained for 193Pb. © 1999 Elsevier Science B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Measurement of the Pb-208(n,p) Tl-208 reaction cross section between 30 and 70 MeV neutron energy

The Pb-208(n,p)(208)T1 reaction cross section has been measured between 30 and 70 MeV neutron energy by the activation method. The results are compared with the predictions of a schematic model which includes contributions from direct reactions and compound nucleus formation

Measurement of cross-sections for the 9Be(n,3n)7Be and 56Fe(n,p)56Mn reactions producing background lines in γ-ray astrophysics

The reactions 9Be(n,3n)7Be and 56Fe(n,p)56Mn were measured between 28 and 68 MeV and at 28 MeV, respectively. These reactions lead to the emission of γ-rays (478, 847, 1811 keV) that may be disturbing in γ-ray astrophysics missions. Consequences regarding the induced background in detectors are drawn. © 1998 Elsevier Science B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe