I. A. Rizvi

MEASUREMENT AND ANALYSIS OF EXCITATION FUNCTIONS AND FORWARD RECOIL RANGE DISTRIBUTIONS IN 12C + 59Co SYSTEM

With the motivation of studying complete and incomplete fusion reactions in a 12C+59Co projectile target system, the excitation functions for (C, p3n), (C, 2p2n), (C, αn), (C, α2n), (C, αp3n) and (C, 2α2n) reactions have been measured up to 80 MeV. The well-known activation technique followed by offline high purity Ge γ-ray spectroscopy was used. The measured experimental values were compared with the statistical model calculations by using the ALICE-91 and CASCADE codes. For the calculations obtained by CASCADE, the variation of parameter Fθ, which is the ratio of actual moment of inertia to the rigid body value have also been studied. Considerable enhancement of the measured excitation functions compared to theoretical predictions for some channels clearly indicates the presence of incomplete fusion with complete fusion in the present projectile energy range. The measurements of forward recoil range distribution of evaporation residues at 80 MeV projectile energy confirm these observations.

REACTION MECHANISMS IN 12C+93Nb SYSTEM: EXCITATION FUNCTIONS AND RECOIL RANGE DISTRIBUTIONS BELOW 7 MeV/u

The experiments were performed to study excitation functions (EFs) of evaporation residues (ERs), i.e. 103,102,101Ag, 101,100,99Pd, 101,100Rh, 97Ru, 96Tc, 95Tc, 94Tc, 93Mom, 92Nbm populated in the reactions induced by 12C on 93Nb for exploring the reaction dynamics involved at energies ≈ 47–75 MeV. The activation technique followed by offline γ-ray spectrometry has been employed to measure EFs. These measurements were simulated with other reported values available in literature as well as with theoretical predictions based on computer code PACE-2. The effect of variation of level density parameter involved in this code has also been studied. An excellent agreement was found between theoretical and experimental values in some of the fusion evaporation channels. However, significant enhancement of cross-section as observed in α-emission channels may be due to incomplete fusion (ICF) process and/or direct reaction process. To confirm the aforesaid reaction mechanism, Recoil Range Distributions (RRDs) of various ERs have been measured at ≈ 80 MeV. Moreover, an attempt is made to separate the percentage relative contributions of complete and incomplete fusion components from the analysis of the measured RRDs data. Further, the relative percentage ICF fraction, also estimated from EFs data, was found to be sensitive with the projectile energy.

Equilibrium and Pre-Equilibrium Studies in Some Alpha Induced Reactions on Rhodium

Excitation functions of the reactions (α, 2 n ), (α, 3 n ), and (α, 4 n ) for 103 Rh have been measured with stacked foil activation technique for the projectile energies below 50 MeV α-particles. A large volume HPGe detector was used. The experimental data were compared with the calculated values obtained from the CASCADE code based on statistical model and ALICE-91 code based on Hybrid and Geometry Dependent Hybrid Models. It is found that the pre-equilibrium contribution is more pronounced in the high energy region of the excitation functions and the experimental data are explained only when the pre-equilibrium emission phenomenon is also taken into account along with the equilibrium decay. The percentage of pre-equilibrium fraction has also been calculated.

Systematics of incomplete fusion probability and its correlation with complete fusion suppression

The mechanism for the suppression of complete fusion, induced by different light alpha cluster projectiles (Z ≤ 10) on 51V target has been investigated through the measurement of break-up of the projectiles into different alpha fragments. The results from the present systems show substantial components from incomplete fusion in addition to complete fusion. The measurements also show significant reduction of complete fusion cross-section above the barrier energies for all the reactions when compared with the theoretical prediction of CCFULL code. CCFULL is a program that calculates fusion cross-sections and mean angular momenta of the compound nucleus under the influence of coupling between the relative motion and several collective nuclear motions. Moreover, measurements also show a systematics in complete fusion suppression with respect to CCFULL calculation, suggesting that the extent of suppression of complete fusion cross-sections is correlated with the alpha Q-value of the projectiles. Also, all the ...

Effect of projectile break-up on incomplete fusion reaction dynamics

Experiments have been carried out to explore the reaction dynamics leading to incomplete fusion of heavy ions at moderate energies. Excitation functions for 176Ta, 175Ta, 174Ta, 173Ta and 166Tm radio-nuclides populated via complete and/or incomplete fusion of 16O with 165Ho have been studied over the wide projectile energy range ≈ 73-105 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 PACE4. 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 this system, and has been found to be sensitive for projectile energy ...