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Evaporation residue (ER) cross-sections have been measured for the 48Ti + 140,142Ce reactions to understand the influence of neutron shell closure on compound nucleus (CN) formation. The measured ER cross-sections for 48Ti + 140Ce (N T = 82) system are found to be very close to those of 48Ti + 142Ce (N T = 84) near the Coulomb barrier. The results show that the effect of shell closure in the target nucleus on fusion cross-sections is negligible for the present systems which can be attributed to the small values of the shell correction energies in the entrance channel. Statistical model calculations are performed to interpret the experimental results. Further, comparison of the present results with those from a reaction with higher mass asymmetry in the entrance channel shows no evidence of quasifission in the present systems. [ABSTRACT FROM AUTHOR]

The fission dynamics has been studied for a near super heavy compound nucleus 260Rf populated through 28Si + 232Th reaction at an excitation energy of 85.7 MeV. Full momentum transfer binary events were separated from the transfer induced fission events. The contribution from transfer induced fission has been found to be 7 ± 2 %. Mas ratio distribution, mass-total kinetic energy (TKE), and mass angle correlation have been extracted for the full momentum transfer events using two body kinematics. The experimentally extracted width of mass distribution is higher than the mass width calculated theoretically using the saddle-point model, which indicates the presence of non-compound nuclear fission in the reaction under study. The mass-TKE distribution obtained for 260Rf nucleus matches with the theoretical predictions from the Viola systematics and GEneral description of Fission observables (GEF) model. The mass-angle distribution for the reaction under study indicates no significant correlation between the mass and emission angles of the fission fragments. [ABSTRACT FROM AUTHOR]

Evaporation residue (ER) cross-sections were measured for 30Si+142Ce reaction at laboratory energies in the range of 105 - 132 MeV using the HYbrid Recoil mass Analyzer (HYRA) at IUAC, New Delhi. The transmission efficiency of the HYRA was estimated using the calibration reaction 28Si+142Ce. Sub-barrier fusion enhancement was observed when compared with the one-dimensional barrier penetration model predictions for the present system. To explore the phenomena responsible for sub-barrier fusion enhancement, coupled-channels calculations were performed using the CCFULL code. The effect of couplings and the role of positive Q -value neutron transfer (PQNT) channels on sub-barrier fusion cross-sections were investigated. Coupled-channels calculations were able to reproduce the data by including the coupling in both projectile and target nucleus along with two neutron-transfer channels having positive Q -value. The measured ER cross-sections were compared with the nearby systems to explore the role of deformation of the colliding nuclei. [ABSTRACT FROM AUTHOR]

Isotopic thin Samarium (Sm) targets of 150–200 μg/cm 2 thickness have been fabricated in high vacuum (HV) environment by thermal evaporation method on carbon (C) backing of 20–25 μg/cm 2 thickness at Inter University Accelerator Centre (IUAC), New Delhi. Salient features of the method used for fabrication of 144 , 154 Sm targets are enumerated below: • A very thin layer of C of thickness 5–10 μg/cm 2 has been evaporated on Sm using electron-gun bombardment technique. • The detailed fabrication procedure along with various challenges faced (peeling off, oxidizing nature of the target etc.) has been discussed in this article. • Energy dispersive X-ray fluorescence (EDXRF) has been used to access the purity, thickness and elemental composition of targets. There is no trace of high Z impurity present in the prepared targets. • These targets have been successfully used in three nuclear physics experiments using the National Array of Neutron Detectors (NAND), HYbrid Recoil Mass Analyzer (HYRA) and General Purpose Scattering chamber (GPSC) at IUAC, New Delhi. [ABSTRACT FROM AUTHOR]

Fabrication of self-supporting 48Ti films of thickness ≈ 500 μ g /cm 2 using 100 mg of the material by electron-beam evaporation technique in a high vacuum environment has been discussed. A simple and novel method of slowly evaporating the enriched material has been adopted in contrast to complex setup modifications utilized in earlier studies. Various techniques employed for successful fabrication of thin films have been discussed. The thickness measurements and characterizations of fabricated thin films have been carried out using advanced techniques viz. , α -transmission method, Rutherford Backscattering Spectrometry (RBS), Energy Dispersive X-ray Spectrometry (EDS), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy Dispersive X-ray Fluorescence (EDXRF). One of the fabricated targets has successfully been used in nuclear physics experiments. • A novel method of slowly evaporating 48Ti target followed by annealing has been discussed for the fabrication of thin films. • e-beam evaporation in high vacuum environment has been followed. • Characterization techniques such as α -transmission method, RBS, EDS, FE-SEM and EDXRF have been used for target characterization. • Targets in the thickness range (319–548) μ g / cm 2 have been fabricated. • Calcium Iodide has been used as a parting agent. [ABSTRACT FROM AUTHOR]

Abstract: Pre-scission neutron multiplicities have been measured for 12C+ 194, 198Pt systems at matching excitation energies at near Coulomb barrier region. Statistical model analysis with a modified fission barrier and level density prescription have been carried out to fit the measured pre-scission neutron multiplicities and the available evaporation residue and fission cross sections simultaneously to constrain statistical model parameters. Simultaneous fitting of the pre-scission neutron multiplicities and cross section data requires shell correction at the saddle point. [Copyright &y& Elsevier]

Abstract: Evaporation residue (ER) cross sections and gamma multiplicity distributions have been measured for 16O+ 184W and 19F+ 181Ta systems in the excitation energy range of 50–90 MeV, leading to the same compound nucleus 200Pb∗. Comparison of experimental results of both the systems shows that ER cross sections and moments of gamma multiplicity distribution of 16O+ 184W system are significantly higher than those of 19F+ 181Ta system at higher excitation energies. Present measurements directly shows the experimental signature of entrance channel effect even with the systems which are not very different with respect to their entrance channel mass asymmetry. It is further demonstrated that the reduction in the ER cross section and moments of spin distribution for 19F+ 181Ta system is mainly due to the suppression of fusion of higher l values. [Copyright &y& Elsevier]

Abstract: The 24Mg+ 24Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV where a narrow and high spin resonance has been reported previously. The decay of the resonance into the inelastic and fusion–evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the γ array CLARA, and, for the fusion–evaporation channels, the Si array EUCLIDES and the γ array GASP. Strong resonant effects have been observed in the inelastic channels involving the and states of the 24Mg ground state band. Weaker effects are also seen in certain fusion–evaporation channels. The properties of the studied resonance are in agreement with molecular model predictions. It is also proposed that the narrow and high spin 24Mg+ 24Mg resonance corresponds to the formation of a fast rotating and highly prolate deformed 48Cr after a Jacobi shape transition and just before fission. [Copyright &y& Elsevier]

An overview of results in fusion studies with stable beams spanning different mass regions and energy ranges is presented. The advantages offered by studying channel coupling effects, involving low-lying excited states of the colliding nuclei, as well as the difficulties in understanding the influence of transfer couplings on fusion, are firstly remarked. The competition of fusion with quasi-fission in heavy systems and the unexpected steep falloff of fusion cross sections at far sub-barrier energies are finally discussed. [Copyright &y& Elsevier]

Abstract: Excited states up to in the neutron-rich nucleus 58Cr have been identified by using a new experimental setup composed of the large acceptance magnetic spectrometer PRISMA and the highly efficient γ-detector array CLARA. Interestingly, the excitation energy sequence of the ground-state band follows the one expected by the dynamical symmetry for a nucleus at the critical point of the shape phase transition from a spherical vibrator () to a γ-soft rotor (). For the first time, in the same physical system, large scale shell-model calculations in the full fp shell are compared to the analytical model results and to the Interacting Boson Model. The theoretical results are in excellent agreement with the present data. [Copyright &y& Elsevier]

The magnetic spectrometer Prisma for heavy ions, at the Laboratori Nazionali di Legnaro, is a device with large acceptance and good resolution. Installation of the spectrometer and its detectors has been recently completed. Preliminary results of the first measurements on multinucleon transfer reactions are reported. [Copyright &y& Elsevier]

The pre- and post-scission neutron multiplicities are measured for the fission of 208Rn, populated with the reactions 30Si + 178 Hf and 48Ti + 160 Gd in the excitation energy range of 54.5 - 80.8 MeV. We found significant differences in the pre-scission neutron multiplicities of these two systems. Also, both the reactions exhibit an enhancement in the pre-scission multiplicity with respect to the existing data for the 16O + 194 Pt reaction populating 210Rn. The measured multiplicities are compared with the theoretical predictions obtained from the Langevin dynamical model for fission. Dynamical simulations are also performed to estimate the capture cross-sections. Contribution of the neutrons, emitted during the fusion process, is shown to be crucial in determining the neutron multiplicities for the present systems. Moreover, in case of the 48Ti + 160 Gd reaction, rapid quasi-fission dynamics prevents neutron emission from the thermalized target-projectile composite. The present measurement helps us to understand the relative importance of fusion and quasi-fission processes and their timescales depending on the entrance channel mass asymmetry. [ABSTRACT FROM AUTHOR]

Abstract: Fission fragment mass angle correlation and mass ratio distributions have been measured for 16O + 194Pt reaction forming the composite system 210Rn in the energy range 75 MeV to 102 MeV in laboratory frame. No mass angle correlation was observed and the mass ratio distributions were compared with theoretical calculations assuming compound nucleus formation. No evidence of quasi-fission process is observed in the reaction. [Copyright &y& Elsevier]