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2017

We propose a study of the B + Pb system at the sub-Coulomb energy of 43 MeV via measurements of the elastic scattering and Be production cross sections. The main goal of this work is to answer a fundamental question concerning the competition between fusion and direct channels below the barrier for a proton halo nucleus like B incident on a heavy target. It is believed from phenomenological predictions that for weakly bound nuclei incident on heavy targets the direct channels exhaust most of the total reaction cross section for incident energies below the Coulomb barrier, with important consequences for both fusion and various astrophysical problems. In this context the sub-barrier breakup and elastic scattering will be investigated for a global understanding of this issue and the relevant channel coupling effects. In addition the elastic scattering measurement will address another fundamental question: how far does the elastic scattering for proton halo nuclei deviate from Rutherfo...

Physical Review C, 2005

We discuss the uncertainties and misinterpretations that may arise from the simultaneous plots of fusion and reaction excitation functions of different systems when weakly bound nuclei are involved, particularly halo nuclei.

Invistigation of fission and evaporation cross sections in a broad range of energies near the Coulomb barrier and up to 200 MeV in the reactions 4,6 He + 209 Bi and 7 Li + 208 Pb were done. The secondary 4,6 He beams were produced using the beam-transport line of the U400M accelerator at FLNR, JINR. The experimental fusion and fission excitation functions obtained for the different reactions 4,6 He + 209 Bi and 7 Li + 208 Pb and leading to the same compound nuclei 213,215 At were analyzed using the PACE-4 and CCFULL.

Progress of Theoretical Physics Supplement, 2004

A new measurement of fusion reactions down to 10 nb has been performed for the system 64 Ni + 64 Ni. Coupled-channels analyses have been carried out for the systems 60 Ni + 89 Y and 64 Ni + 64 Ni. They demonstrate that coupled-channels calculations are unable to reproduce the unexpected steep falloff of the cross sections at extreme sub-barrier energies. Heavy-ion fusion excitation functions are also analyzed in terms of the S factor, as this offers a pragmatic way to study fusion behavior in the energy regime of interest. It is shown that the steep falloff in cross section observed in several heavy-ion systems translates into a maximum of the S factor. The energies where the maximum occurs can be parameterized with a simple empirical formula. The parameterization, which is derived here for rather stiff heavy-ion systems, provides also an upper limit for reactions involving softer nuclei.

Fission and evaporation cross sections were measured in a broad range of energies near the Coulomb barrier and up to 180 MeV in the reactions 46He+U'9Bi and 'Li+2"8Pb. The secondary 4.hHe beams were produced using the beam-transport line of the U400M accelerator at FLNR, JINR. The experimental fusion and fission excitation functions obtained for the different reactions 4He+2"9Bi, 'He+*"'Bi and 7Li+Z'1XPb and leading to the same composite nuclei 2".2'5At were analyzed using the PACE-4 and CC codes from the point of view of the fusion reaction mechanism induced by weakly bound nuclei. The comparison between the fission and fusion excitation functions for the three reactions 46He+211yBi and 7Li+2"8Pb has shown that they are the same within the experimental error for a broad range of energy.

The European Physical Journal A, 2000

The 7 Li + 11 B reaction has been investigated in the energy range 5.5 MeV < E lab < 19 MeV, by detecting γ-ray resulting from the de-excitation of evaporation residues. Statistical compound-nucleus calculations have been performed in order to extract both the cross-sections of individual exit channels and the fusion cross-section of the system. The total angular momentum that the compound nucleus 18 O can support has been deduced and is seen to exhibit saturation for a limiting value of 8.5h at the high-energy extreme. The results are discussed in terms of the entrance channel and statistical yrast line limitations.

Physics Letters B, 2006

Complete and incomplete fusion cross sections for the 9 Be + 144 Sm reaction have been measured at near-barrier energies, using the delayed X-ray detection technique. At above-barrier energies these show a suppression of complete fusion for this weakly bound projectile on an intermediate mass target. The suppression factor, attributed to 9 Be break-up, was deduced from a comparison of complete fusion yields with coupled-channels calculations, and appears consistent with measured incomplete fusion product yields. At ∼ 10%, it is considerably smaller than the value of ∼ 30% previously found for a 208 Pb target. Simultaneous measurements of elastic and inelastic scattering permit a clearer picture of the reaction mechanisms.

2015

The reaction 34 S + 186 W at E lab =160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF−γ coincidence method is of better use then the γ − γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

Physical Review C

Production cross sections for nuclei fragments from the interaction of 11 B ions with 209 Bi and 181 Ta targets, in the intermediate energy regime, have been obtained with the induced-activity method and offline γ spectroscopy. The mass-yield distributions were obtained and the fission process was investigated by using the multimodal fission approach in the case of the 209 Bi target and a pure symmetric distribution for the 181 Ta target. The fissilities were deduced for both targets and further compared to the data for proton-induced reactions. The relative values of the linear momentum imparted to the targets were derived from the cross section data.

Physical Review C, 2008

Experiments have been carried out to explore the reaction dynamics leading to incomplete fusion of heavy ions at moderate excitation energies. Excitation functions for 168 Lu m , 167 Lu, 167 Yb, 166 Tm, 179 Re, 177 Re, 177 W, 178 Ta, and 177 Hf radio-nuclides populated via complete and/or incomplete fusion of 16 O with 159 Tb and 169 Tm have been studied over the wide projectile energy range E proj ≈ 75-95 MeV. Recoil-catcher technique followed by off-line γ-spectrometry has been employed in the present measurements. Experimental data have been compared with the predictions of theoretical model code PACE2. The experimentally measured production cross sections of α-emitting channels were found to be larger as compared to the theoretical model predictions and may be attributed to incomplete fusion at these energies. During the analysis of experimental data, incomplete fusion has been found to be competing with complete fusion. As such, an attempt has been made to estimate the incomplete fusion fraction for both the systems, and has been found to be sensitive for projectile energy and mass asymmetry of interacting partners.