M. H. Rashid

Investigation of incomplete fusion in 20Ne + 55Mn reactions at 3–8 MeV/nucleon

The excitation functions of radio-nuclides have been measured for the 20Ne + 55Mn system in the energy range ≈51–164 MeV by employing the recoil catcher technique followed by off-line gamma-ray spectrometry. It has been observed that some of the residues produced directly via complete and/or incomplete fusion (ICF) give rise to independent yield while some of the residues are produced in the decay of higher charge precursor isobars through β+ and/or electron capture and give rise to cumulative yield. Independent yields of radio-nuclides 71, 70As, 69, 67Ge and 67, 66Ga have been separated out from the measured cumulative yields. The measured excitation functions are then compared with statistical model code PACE-2. It has been observed that excitation functions of the measured complete fusion channels are in good agreement with theoretical predictions. However, a significant enhancement in the measured excitation functions for the residues, produced in the break-up of the projectile into α-clusters, has been observed. This enhancement may be attributed to the ICF process. Moreover, ICF-fraction has also been calculated by dividing the ICF-cross-section to the total fusion cross-section and found to increase with the projectile energy as well as with the entrance channel mass-asymmetry of the interacting partners.

EXCITATION FUNCTIONS OF α-INDUCED REACTIONS IN COBALT AND PRE-EQUILIBRIUM EFFECTS

Excitation functions for the reactions (α,2n), (α,αn), (α,α2n), (α,α3n) and (α,2pn) have been measured using 57Co as a target up to 50 MeV α-particle energy. The stacked foil activation technique and γ-ray spectroscopy method has been employed. Measured excitation functions are compared with the geometry dependent hybrid (GDH) model. A comparison shows that the pure equilibrium (EQ) compound reaction mechanism is incapable of reproducing the experimental data while the pre-equilibrium (PE) reaction mechanism along with equilibrium (EQ) decay, where it is considered that pre-equilibrium emission of particles take place prior to the establishment of the thermodynamical equilibrium of the system, is able to reproduce the experimental data. The GDH model code ALICE-91 has been used for theoretical calculations. A value of initial exciton number n0=4 with configuration (2 neutron + 2 proton + 0 hole) has been found to give the satisfactory reproduction of experimental excitation functions.

Measurement of excitation functions and mean projected recoil ranges of nuclei in12C-induced reactions on vanadium

Excitation function and mean projected recoil ranges of nuclei produced in the12C-induced reactions on51V target were measured by conventional stacked foil and thick-target thick-recoil-catcher technique for bombarding energiesE ≤ 84 MeV for12C ion beam. The measured recoil ranges are converted to momentum transfer. Information on momentum transfer was used to get clues about some aspects of the interaction such as complete fusion which corresponds to full momentum transfer and incomplete fusion reaction mechanism. The measured excitation functions are compared with the calculation based on the statistical model which describes only equilibrium decay of the compound nucleus using the Cascade code and the geometry dependent hybrid model which describes equilibrium as well as pre-equilibrium decay of the compound nucleus using the Alice/91 code. The measured excitation functions and average ranges of the radioisotope products of the reactions12C on51V indicate that the three separate reaction mechanisms could be attributable to complete fusion of12C, incomplete fusion of8Be and incomplete fusion of4He respectively with the target. The8Be and4He are the break-up component of12C into8Be +4He. The predictions of the codes, especially the Cascade, generally agree with the measured cross-sections which could be attributed to complete fusion of12C with the target51V.

An overview on incomplete fusion reaction dynamics at energy range ∼ 3-8 MeV/A

The information of ICF reaction has been obtained from the measurement of excitation function (EF) of ERs populated in the interaction of 20Ne & 16O on 55Mn, 159Tb & 156Gd targets. Sizable enhancement in the measured cross-sections has been observed in α-emitting channels over theoretical predictions, which has been attributed to ICF of the projectile. In order to confirm the findings of the measurements and analysis of EFs, the forward recoil range distributions of ERs populated in 20Ne+159Tb (E ∼165MeV) and 16O+156Gd (E ∼ 72, 82 & 93MeV) systems, have been measured. It has been observed that peaks appearing at different cumulative thicknesses in the stopping medium are related with different degree of linear momentum transfer from projectile to target nucleus by adopting the break-up fusion model consideration. In order to deduce the angular momentum involved in various CF and / or ICF reaction products, spin distribution and side-feeding intensity profiles of radio-nuclides populated via CF and ICF cha...

Investigation of complete and incomplete fusion dynamics of 20Ne induced reactions at energies above the Coulomb barrier

Experiment has been performed to explore the complete and incomplete fusion dynamics in heavy ion collisions using stacked foil activation technique. The measurement of excitation functions of the evaporation residues produced in the 20Ne+165Ho system at projectile energies ranges ≈ 4-8 MeV/nucleon have been done. Measured cumulative and direct cross-sections have been compared with the theoretical model code PACE-2, which takes into account only the complete fusion process. The analysis indicates the presence of contributions from incomplete fusion processes in some α-emission channels following the break-up of the projectile 20Ne in the nuclear field of the target nucleus 165Ho.

Reaction mechanisms in the system {sup 20}Ne+{sup 165}Ho: Measurement and analysis of forward recoil range distributions

Keeping in view the study of complete and incomplete fusion of heavy ions with a target, the forward recoil range distributions of several evaporation residues produced at 164 MeV {sup 20}Ne-ion beam energy have been measured for the system {sup 20}Ne+{sup 165}Ho. The recoil catcher activation technique followed by off-line gamma spectroscopy has been employed. Measured forward recoil range distributions of these evaporation residues show evidence of several incomplete fusion channels in addition to complete fusion. The entire and partial linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The results indicate the occurrence of incomplete fusion involving the breakup of {sup 20}Ne into {sup 4}He+{sup 16}O and/or {sup 8}Be+{sup 12}C followed by fusion of one of the fragments with target nucleus {sup 165}Ho. Complete and incomplete fusion reaction channels have been identified in the production of various evaporation residues and an attempt has been made to separate out relative contributions of complete and incomplete fusion components from the analysis of the measured recoil range distribution data. The total contribution of complete and incomplete fusion channels has also been estimated.

Measurement and Analysis of Alpha Particle Induced Reactions on Praseodymium

Excitation functions (EFs) for the reaction 141 Pr(α, n ) 144 Pm and 141 Pr(α,2 n ) 143 Pm have been measured using 141 Pr as a target up to 50 MeV α-particle energy. Stacked foil activation technique and γ-ray spectroscopy using 100 cm 3 Ge (Li) detector, has been used. Excitation functions are also calculated theoretically using Blanns geometry dependent hybrid (GDH) model code ALICE-91, with and without inclusion of pre-equilibrium particle emission. It has been observed that high-energy tails of the EFs are dominated by pre-equilibrium reaction mechanism. With the accepted set of input parameter, initial exciton number n 0 =4 (2 p +2 n +0 h ), a good qualitative agreement is found. However, quantitative agreement for this magic nucleus 141 Pr is also good when theoretical calculations are normalized by a multiple factor of 0.5.