Propriétés spectroscopiques de U4+ dans ThBr4

L'indexation de raies à zéro phonon du spectre d'absorption de ThBr4 : U4+ est discutée, compte tenu du spectre de vibration de la matrice et des spectres d'émission de ces monocristaux excites par laser

Microscopic description of cluster radioactivity in actinide nuclei

Cluster radioactivity is the emission of a fragment heavier than an α particle and lighter than mass 50. The range of clusters observed in experiments goes from 14C to 32Si while the heavy mass residue is always a nucleus in the neighborhood of the doubly-magic 208Pb nucleus. Cluster radioactivity is described in this paper as very asymmetric nuclear fission. A new fission valley leading to a decay with large fragment mass asymmetry matching the cluster radioactivity products is found. The mass octupole moment is found to be more convenient than the standard quadrupole moment as the parameter driving the system to fission. The mean-field Hartree-Fock-Bogoliubov theory with the phenomenological Gogny interaction has been used to compute the cluster emission properties of a wide range of even-even actinide nuclei from 222Ra to 242Cm, where emission of the clusters has been experimentally observed. Computed half-lives for cluster emission are compared with experimental results. The noticeable agreement obtained between the predicted properties of cluster emission (namely, cluster masses and emission half-lives) and the measured data confirms the validity of the proposed methodology in the analysis of the phenomenon of cluster radioactivity. A continuous fission path through the scission point has been described using the neck parameter constraintThe work of LMR was supported by Ministerio de Ciencia e Innovacion (Spain) Grants No. FPA2009-08958 and No. FIS2009-07277, as well as by Consolider-Ingenio 2010 Programs CPAN CSD2007-00042 and MULTIDARK CSD2009- 00064. The work of MW was supported by Ministerstwo Nauki i Szkolnictwa Wyzszego (Poland) under Grant No. N N202 23113

Low energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let

New measurement of exotic decay of 225^{225}Ac by 14^{14}C emission

The branching ratio of $^{225}$Ac decay by emission of $^{14}$C was remeasured under improved experimental conditions by using a radioactive source produced at the ISOLDE mass-separator at CERN and a nuclear track detector technique. The result, B=$\lambda_{^{14}\textrm{C}} / \lambda_{\alpha} = (4.5 \pm 1.4) 10^{-12}$, is consistent with the anomalously high value obtained in the 1993 experiment thus confirming the importance of nuclear structure effects in this exotic decay

Section efficace de formation de l'isotope de protactinium de masse 226 produit dans le thorium par des protons de 155 MeV

The value of the cross-section of 226Pa production by the 232Th(p, 7n) reaction for 155 MeV protons, obtained by comparison with 227Pa, is 1 ± 0.3 mb.La valeur de la section-efficace de formation de 226Pa par la réaction 232Th(p, 7n), déterminée par rapport à celle de 227Pa, est, à 155 MeV, de 1 ± 0.3 mb