nan Unnati

A STUDY OF EXCITATION FUNCTIONS FOR SOME RESIDUES PRODUCED IN THE SYSTEM 14N+128Te IN THE ENERGY RANGE ≈ 64–90 MeV

The excitation functions for eight reactions produced in the interaction of 14N+128Te have been measured in the energy range ≈ 64–90 MeV using the activation technique. To the best of our knowledge these measurements have been performed for the first time. The measured excitation functions are compared with theoretical calculations done using the computer programs ALICE-91 and PACE. The effect of the variation of various program parameters on calculated excitation functions have been studied. The present analysis indicates that complete fusion, incomplete fusion and pre-equilibrium emission processes play important roles in these reactions.

PRODUCTION OF FISSION-LIKE EVENTS AFTER COMPLETE AND/OR INCOMPLETE FUSION OF 16O WITH 159Tb AND 169Tm AT E/A ≈ MeV

With a view to study heavy-ion induced fission after complete and/or incomplete fusion reactions, experiments have been performed at the Inter-University Accelerator Center (IUAC), New Delhi, India. The production cross-sections for more than 40 fission-like events (25 ≤ Z ≤ 45) produced in 16O+159Tb and 16O+169Tm systems, respectively, at E/A = 5.6 and 5.9 MeV have been measured using the recoil-catcher technique followed by off-line γ-spectroscopy. The analysis of the data indicates that fission is one of the competing modes of de-excitation of excited composite system formed via complete and/or incomplete fusion processes, where the evaporation of light nuclear particle(s) are more likely to be expected. Attempts have also been made to study isotopic yield distributions of Yttrium (83, 84m, 85, 87mY) and Strontium (80, 81, 83, 85mSr) isotopes in 16O+159Tb system, and Indium (105, 107, 108, 110In) and Technetium (99m, 101, 104, 105Tc) isotopes in 16O+169Tm system. The statistical analysis of the isotopic yield distribution has also been carried out to determine the most probable values of mass and charge of fission-like events in two systems.

Observation of incomplete fusion reactions at l < l crit

In order to understand the presence of incomplete fusion at low energies i.e. 4-7MeV/nucleon & also to study its dependence on various entrance-channel parameters, the two type of measurements (i) excitation function for 12C+159Tb, and (ii) forward recoil ranges for 12C+159Tb systems have been performed. The experimentally measured excitation functions have been analyzed within the framework of compound nucleus decay using statistical model code PACE4. Analysis of data suggests the production of xn/px)n-channels via complete fusion, as these are found to be well reproduced by PACE4 predictions, while, a significant enhancement in the excitation functions of α-emitting channels has been observed over the theoretical ones, which has been attributed due to the incomplete fusion processes. Further, the incomplete fusion events observed in case of forward recoil range measurements have been explained on the basis of the breakup fusion model, where these events may be attributed to the fusion of 8Be and/or 4He ...

Low energy in-complete fusion: The α-Q-value systematics

In the present work, the in-complete fusion probability has been deduced for 12C+159Tb and 13C+159Tb systems in the energy range ≈ 4-7 MeV/nucleon. The activation technique followed by off-line γ-rays spectroscopy has been used. The results have been compared with the predictions of statistical model code PACE4, which is based on the compound nucleus decay. The ratio of the sum of cross-sections of all measured xn, pxn channels to their corresponding PACE4 predictions are found to be lying close to unity throughout the studied energy range for both the systems, indicating their population via fusion evaporation channels followed by CF processes only. However, the ratio of the sum of cross-sections of all experimentally measured xn, pxn and αxn-channels to their corresponding PACE4 calculations, display significant enhancement over the unity line, indicating the onset and presence of in-complete fusion processes at these energies. The comparison of experimentally measured and systematically deduced in-comp...

Identification of fission-like events in the {sup 16}O + {sup 181}Ta system: Mass and isotopic yield distribution

In this paper, nuclear reaction cross sections for 24 fission-like fragments (30{<=}Z{<=}60) have been measured for the 6.5 MeV/A {sup 16}O + {sup 181}Ta system. The recoil-catcher activation technique was employed followed by off-line {gamma} spectroscopy. The isotopic yield distributions for yttrium and indium isotopes have been obtained from the experimental data. The variance of the presently measured isotopic yield distributions have been found to be in agreement with the literature values. However, the variance of the mass distribution of fission residues has found to be narrower as compared to other relatively heavier systems. A self-consistent approach to determining the isobaric charge dispersion parameters has been adopted. The measured fission cross sections at 97 and 100 MeV are satisfactorily described by a statistical model code. An attempt has been made to explain the production cross sections of intermediate mass residues in the fission of heavy residues populated via complete and/or incomplete fusion processes.

Large pre-equilibrium contribution in {alpha}+{sup nat}Ni interactions at {approx_equal}8-40 MeV

To investigate pre-equilibrium emission of light nuclear particle(s), an experiment has been performed using a beams at the Variable Energy Cyclotron Center (VECC), Kolkata, India. In the present work, excitation functions for 58 Ni(α, p) 61 Cu, 58 Ni(α, pn) 60 Cu, 60 Ni(α, p2n) 61 Cu, 60 Ni(α, n) 63 Zn, 60 Ni(α, 2n) 62 Zn, 61 Ni(α, 3n) 62 Zn, and 61 Ni(α, 2n) 63 Zn reactions have been measured by using the stacked foil activation technique followed by off-line γ-ray spectroscopy. Experimentally measured excitation functions have been compared with the prediction of the theoretical model code ALICE-91 with and/or without the inclusion of pre-equilibrium emission. Analysis of the data suggests that an admixture of both equilibrium and pre-equilibrium emission is needed to reproduce experimental data at energies ≈8-40 MeV and reveals significant contribution from pre-equilibrium emission. An attempt has also been made to estimate the pre-equilibrium contribution, which has been found to depend on projectile energy and on number of emitted particle(s).