M. Afzal Ansari

Excitation Function Studies of (α, xpyn) Reactions for 63,65Cu and Pre-Equilibrium Effect

Excitation functions of tone reactions (α, n), (α, 2n), (α, pn) for 63 Cu and (α, n), (α, 2n), (α, 3n), (α, p3n) for 65 Cu have been measured with stacked foil activation techniques for projectile energies below 40 MeV α-particle. A large-volume Ge(Li) detector was used. Theoretical excitation functions for the above reactions have also been calculated with and without inclusion of pre-equilibrium particle emission in the framework of a geometry-dependent-hybrid model using ALICE/LIVERMORE 82 computer code. It is found that the pre-equilibrium contribution is more pronounced in the high-energy tail region of the excitation function and the experimental data are explained only when the pre-equilibrium emission phenomena is also taken into account along with the equilibrium decay.

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.

Radiative capture cross-sections of isotopes of Gd, Sm and V between 1 and 3 MeV

Abstract Fast-neutron radiative capture cross-sections have been measured relative to the 127 I(n, γ) 128 I reaction cross-section using the comparative activation technique for 160 Gd, 154 Sm and 51 V (using enriched isotopes and Specpure samples) at five different neutron energies between 1 and 3 MeV. The cross-section for 160 Gd is reported for the first time in the above energy region. Experimental values are compared with the statistical-model calculations.

Complete and Incomplete Fusion Reactions in 16O+45Sc System: Measurement and Analysis of Excitation Functions below 7 MeV/Nucleon

Complete and incomplete fusion reactions study in heavy ion induced reactions, by 16 O ions on 45 Sc at incident energies ranging between 39 and 114 MeV have been done using the activation technique followed by γ-ray spectrometry. The excitation functions for eleven reactions have been measured using this technique. A comparison of the experimental data has been made with the calculations based on statistical model. Excitation function measurement of various reactions, for the above projectile–target system is being reported for the first time. Complete and incomplete fusion reaction channels have been identified in the production of various residual nuclei, by analysing the experimental data. The results indicate the occurrence of incomplete fusion involving breakup of 16 O into 4 He+ 12 C and 8 Be+ 8 Be followed by fusion of one of the fragments with target nucleus 45 Sc.

Pre-equilibrium decay process in the alpha induced reactions of silver isotopes

Abstract Excitation functions for the reactions 107Ag(α,n)110In, 107Ag(α,2n)109In, 109Ag(α,2n)111In, 109Ag(α,3n)110In and 109Ag(α,4n)109In have been measured from 13 to 50 MeV with the help of the stack-foil technique. Since the silver target used has two odd mass stable isotopes of about equal abundance, 107Ag (51.83%) and 109Ag (48.17%), in some cases the residual nuclei are the same through different reaction channels but the Q-values are different. In these cases the experimental cross-sections are separated out by using the ratio of theoretical cross-sections of the same reaction. The experimental results were compared with calculated values obtained by means of the geometry-dependent hybrid (GDH) model. The initial exciton number n0 = 4 with different configurations was tested. It was found that the configuration (2n + 2p + 0h) appears to give a good fit to the experimental data.

Isomeric cross-sections of In and Rh at neutron energies of a few MeV

Abstract Neutron capture cross-sections are measured at five different neutron energies (1.07 ± 0.20, 1.48 ± 0.18, 1.89 ± 0.17, 2.30 ± 0.16 and 2.85 ± 0.15 MeV) for the isomeric states of In and Rh. The comparative γ-activation technique has been used. The present results are compared with previous data wherever available.

Non-equilibrium reaction mechanism in alpha-particle induced excitation function for 209Bi up to 60 MeV

Abstract Excitation functions (α, 3n) and (α, 4n) for 209Bi have been measured up to 60 MeV α-particle energy. The excitation functions are measured at 15α-particle energies by a stack foil technique in two steps. Excitation functions for the above two reactions have been reported for the first time in the energy range from 40 to 60 MeV. The measured experimental values are compared with the geometry-dependent hybrid (GDH) model in which the emission of particles prior to the equilibrium decay is taken into account whenever the interaction of projectile with the target nucleus is considered. It is found that the compound nucleus decay mechanism alone is unable to explain the experimental trend of our data. The initial exciton number 4 with different configurations has been tested and it is concluded that the configuration (2n + 2p + 0h) gives the best fit to the experimental data.

Fast neutron radiative capture cross-sections in fission product isotopes of neodymium

Fast neutron radiative capture cross-sections for Nd-148 and Nd-150 have been measured at about 10 neutron energies between 0.46 and 3.44 MeV using enriched isotopes and the activation technique. Experimental results are also compared with the theoretical one using FISPRO II computer code.

Measurement and analysis of excitation functions for alpha induced reactions on iodine and cesium

The excitation functions for the reactions127I(α, 2n)129Cs,127I(α, 4n)127Cs,133Cs(α, 2n)135La and133Cs(α, 4n)133La have been measured up to ≈50 MeVα-particle energy using the stacked foil activation technique. Measured excitation functions are compared with pre-equilibrium geometry dependent hybrid model calculations. It has been found that theoretical calculations using an initial exciton numbern0=4 (2p+2n+0h) give good agreement with experimental excitation functions.

181Ta(n, α)178mLu, 178Lu reactions and isomeric states of 17871Lu107

Abstract The cross sections for the production of 25 min and 5 min activities due to the isomeric states of 178 Lu, produced by the 181 Ta(n, α) reaction, have been measured at four neutron energies in the keV region. From a study of σ 5 min (n, α)/σ 25 min (n, α) versus E n , an attempt has been made to assign spins to the 25 min and 5 min isomeric states of 178 Lu.