Light-particle emission from the fissioning nuclei 126Ba, 188Pt and (266,272,278)/110: theoretical predictions and experimental results

We present a comparison of our model treating fission dynamics in conjunction with light-particle (n, p, alpha) evaporation with the available experimental data for the nuclei 126Ba, 188Pt and three isotopes of the element Z=110. The dynamics of the symmetric fission process is described through the solution of a classical Langevin equation for a single collective variable characterizing the nuclear deformation along the fission path. A microscopic approach is used to evaluate the emission rates for pre-fission light particles. Entrance-channel effects are taken into account by generating an initial spin distribution of the compound nucleus formed by the fusion of two deformed nuclei with different relative orientations

Halo structure of 14Be

The first kinematically complete breakup reaction study of 14Be was carried out. The two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra for reactions on C and Pb were measured and the electromagnetic component of the dissociation (EMD) contributions deduced. Comparison with model calculations suggest that the configuration of the halo neutrons contains a large v(2s 1/2 )2 admixture.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Two-neutron interferometry as a probe of the nuclear halo

The technique of intensity interferometry is proposed as a probe of the spatial configuration of two-Neutron haloes. After exploring the sensitivity of interferometry to the n-N configuration, it is demonstrated that the application of the standard method for constructing the correlation function is not valid for halo neutrons. A new iterative method is presented and applied to measurements of the dissociation of 6He, 11Li and 14Be. The correlation functions for these systems have thus been extracted for the first time and the corresponding root-Mean-Square n-n separations estimated. The results are in agreement with the predictions of available three-Body models. (C) 2000 Published by Elsevier Science B.V.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fission and quasifission modes in heavy-ion-induced reactions leading to the formation of Hs*

Mass and energy distributions of binary reaction products obtained in the reactions Ne22+Cf249,Mg26+Cm248, S36+U238, and Fe58+Pb208 have been measured. All reactions lead to Hs isotopes. At energies below the Coulomb barrier the bimodal fission of Hs*, formed in the reaction Mg26+Cm248, is observed. In the reaction S36+U238, leading to the formation of a similar compound nucleus, the main part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier fusion-fission is the main process leading to the formation of symmetric fragments for both reactions with Mg and S ions. In the case of the Fe58+Pb208 reaction the quasifission process dominates at all measured energies. © 2011 American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fission and quasifission modes in heavy-ion-induced reactions leading to the formation of Hs*

Mass and energy distributions of binary reaction products obtained in the reactions 22Ne+249Cf,26Mg+248Cm, 36S+238U, and 58Fe+208Pb have been measured. All reactions lead to Hs isotopes. At energies below the Coulomb barrier the bimodal fission of Hs*, formed in the reaction 26Mg+248Cm, is observed. In the reaction 36S+238U, leading to the formation of a similar compound nucleus, the main part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier fusion-fission is the main process leading to the formation of symmetric fragments for both reactions with Mg and S ions. In the case of the 58Fe+208Pb reaction the quasifission process dominates at all measured energies

Probing fission time scales with neutrons and GDR gamma rays

The time scales for nuclear fission have been explored using both pre- and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV /sup 16/O+/sup 176/Yb and /sup 208/Pb and 104-MeV /sup 4/He+/sup 188/Os and /sup 209/Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF/sub 2/ array. The pre- and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, gamma , and fission time scales. The gamma values ranged from 7 to 20, while the fission times were (31-105)*10/sup -21/s

Prefission neutron multiplicities and the fission modes of 226^{226}Th

The neutron spectra associated to the two fission modes of 226Th have been measured in coincidence with the fragment yields of the 18O + 208Pb reaction at Elab = 78 MeV. The pre- and post-fission multiplicities and temperatures have been extracted. Surprisingly, the prefission neutron multiplicities associated with the asymmetric mode are larger than those associated with the symmetric mode.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Prefission neutron multiplicities and the fission modes of

The neutron spectra associated to the two fission modes of 226Th have been measured in coincidence with the fragment yields of the 18O + 208Pb reaction at $E_{\rm lab}=78\;\rm MeV$. The pre- and post-fission multiplicities and temperatures have been extracted. Surprisingly, the prefission neutron multiplicities associated with the asymmetric mode are larger than those associated with the symmetric mode.