Search

A systematic analysis of the fusion cross sections around the Coulomb barrier energies with stable weakly bound ($^{6}$Li,$^{7}$Li,$^{9}$Be) and strongly bound $^{12}$C projectiles on various targets was performed by using neutron flow model and coupled channels approach. The analysis show that both the models are successful in explaining the near barrier fusion data. Further, it is also observed that the collective degrees of freedom as well as the neutron flow influence the near barrier fusion process involving weakly bound projectiles., Comment: 6 pages, 4 figures

Studies in the past have demonstrated that complete fusion and incomplete fusion (ICF) dynamics are both significant just above the Coulomb barrier, yet the dynamics of ICF are elusive since they are so complex below 10 MeV/nucleon. In order to investigate low-energy ICF dynamics, we measured the forward recoil range distribution (FRRD) of evaporation residues (ERs) populated in the system 14N + 169Tm at energy ≈5.9 MeV/nucleon. A stack target-catcher activation technique followed by offline-γ-spectroscopy was used to estimate the FRRD of the ERs. In order to investigate a new parameter for describing ICF dynamics, the ICF fraction (F ICF(%)) for the present system was estimated from the range-integrated cross-sections and compared with other systems in the literature. The FRRD and range integrated cross-sections of seven ERs have been estimated experimentally. These cross-section results agree well with the experimental results obtained from the excitation functions. On re-investigation of entrance channel systematics for Q α -value of projectile, mass-asymmetry (μ MA), and Coulomb factor (Z P Z T), it has been found that the Q α -value systematic for 14N is not valid at all projectile energies. The FRRD measurement is one of the direct methods available to probe the complete and ICF contributions in ERs at low projectile energy. It has also been observed that the dynamics of ICF are not only dependent on the parameters of one entrance channel but on multiple entrance channels. We have also introduced the entrance channel parameter zeta (ζ) for the first time in ICF reactions to see the combined effect of mass-asymmetry (μ MA) and Z P Z T, as this parameter is better suited than μ MA and Z P Z T individually and has a linear dependency on F ICF(%).

The $^{8}\mathrm{Li}+^{58}\mathrm{Ni}$ collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Quasielastic angular distributions and the singles $^{7}\mathrm{Li}$ angular and energy distributions are presented. Coupled-reaction channels (CRC) calculations, which include the coupling of the elastic channel to $^{59}\mathrm{Ni}=^{58}\mathrm{Ni}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}n$ states above and below the neutron threshold, provide a simultaneous description of the quasielastic and transfer distributions and evidence the strong effect of the one-neutron transfer/breakup channels on the quasielastic scattering. The $^{7}\mathrm{Li}$ angular and energy distributions have been also successfully analyzed combining the continuum discretized coupled channels (CDCC) method, for the elastic breakup, and the IAV model of Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)], for the nonelastic breakup. These calculations indicate that most of the $^{7}\mathrm{Li}$ yields are due to nonelastic breakup contributions (transfer), whereas elastic breakup plays a minor role.

In this contribution, we report on effects due to the cluster configuration of boron isotopes, \(^8\)B, \(^{10}\)B, \(^{11}\)B and \(^{12}\)B, in the elastic scattering on \(^{58}\)Ni target at energies close to the Coulomb barrier. The results of coupled channel calculations, where the different configurations of the boron isotopes, \(^8\)B \(=\) \(^7\)Be\(+\)p, \(^{10}\)B \(=\) \(^6\)Li\(+\) \(\alpha \), \(^{11}\)B \(=\) \(^7\)Li\(+\) \(\alpha \) and \(^{12}\)B \(=\) \(^{11}\)B\(+\)n, have been attributed to different effects in the angular distributions for the elastic scattering process, are present.

Alpha particle energy distributions in the 6He+120Sn collision have been measured at 7 bombarding energies above the Coulomb barrier. A phenomenological analysis of the centroids of the experimental distributions was performed and compared with the expected alpha-particle energies from breakup and neutron transfer reactions. Q-optimum conditions were determined using the Brinks formula for the di-neutron transfer reaction. A comparison of the measured alpha-particle production cross-sections with Continuum Discretized Coupled Channels (CDCC) calculations for breakup is presented. Fundacao de Amparo `a Pesquisa no Estado de Sao Paulo 2013/22100-7, 2014/19666-1 Conselho Nacional de Desenvolvimento Cientıfico e Tecnologico 308935/2018-7 Ministerio de Economía y Competitividad FIS2017-88410-P European Union 654002

Elastic scattering and transfer cross sections for the $^{7}\mathrm{Be}+^{9}\mathrm{Be}$ system have been measured at ${E}_{\mathrm{lab}}=23.1\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ using the $^{7}\mathrm{Be}$ radioactive secondary beam produced at Radioactive Ion Beams in Brazil facility at the University of S\~ao Paulo. The elastic scattering has been measured by detecting the $^{7}\mathrm{Be}$ scattered at forward angles in the laboratory system. The transfer reaction $^{9}\mathrm{Be}(^{7}\mathrm{Be},^{9}\mathrm{Be})^{7}\mathrm{Be}$ was identified by detecting the $^{9}\mathrm{Be}$ scattered at the same laboratory angles. The elastic angular distribution has been analyzed by optical model calculations using a Woods-Saxon form factor whose parameters have been varied to best reproduce the experimental data at forward angles. Coupled reaction channels calculations (CRC) have been performed to describe the transfer, considering the coupling to the transfer channel and including contributions to the ground state and to the first excited state of $^{7}\mathrm{Be}(1/2\ensuremath{-};429\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$) in the final state. The spectroscopic amplitudes used in the CRC calculation have been derived from shell-model calculations. Similar CRC calculations were applied to existing $^{9}\mathrm{Be}(p,t)^{7}\mathrm{Be}$ data to check the consistency of our results results for the ($^{7}\mathrm{Be},^{9}\mathrm{Be}$) transfer reaction.

Elastic scattering of a radioactive neutron-rich boron isotope, $^{12}\mathrm{B}$, has been measured for the first time. Angular distributions for the elastic scattering of $^{12}\mathrm{B}+^{58}\mathrm{Ni}$ have been measured at ${\mathit{E}}_{\mathrm{Lab}}=30.0$ and 33.0 MeV, which are just above the Coulomb barrier (${\mathit{V}}_{\mathrm{B}}=24$ MeV). The obtained angular distributions were analyzed in terms of the large-scale coupled channel (CC) and coupled reaction channel (CRC) calculations, where several inelastic transitions for the target, as well as the most relevant transfer reactions, have been included in the coupling matrix elements. The roles of the spin reorientation and spin-orbit interaction in the reaction mechanism were also investigated. The one-neutron transfer reaction through a coupled reaction calculation had some effect on the elastic scattering of the system studied.

Absolute cross sections for 22 fissionlike fragments concerning their decay mode via independent and cumulative cross sections have been measured at four projectile energies, i.e., $82.2\ifmmode\pm\else\textpm\fi{}0.8,\phantom{\rule{0.28em}{0ex}}79.18\ifmmode\pm\else\textpm\fi{}0.82,\phantom{\rule{0.28em}{0ex}}76.8\ifmmode\pm\else\textpm\fi{}1.2$, and $72.9\ifmmode\pm\else\textpm\fi{}0.91\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$. The recoil-catcher activation technique followed by offline $\ensuremath{\gamma}$-ray spectrometry was employed. The isotopic yield distribution and the variance for indium isotopes have been obtained from the experimental data and were found to be in agreement with the literature values. The fissionlike fragments mass distribution is found to be a single-peaked Gaussian distribution and confirms their population via deexcitation of the compound nucleus. The mass distribution variance is found to be narrower and exponentially increases as compared to relatively heavier systems at above 20% of the Coulomb barrier. A self-consistent approach for determining the isobaric charge dispersion parameters has been adopted. The present paper suggests that fission is one of the competing modes at low energies other than complete fusion and incomplete fusion processes.

A large yield of $\ensuremath{\alpha}$ particles produced in the $^{120}\mathrm{Sn}(^{6}\mathrm{He},\ensuremath{\alpha})$ reaction was measured at 20.3-, 22.2-, 22.4-, and 24.5-MeV bombarding energies. The $\ensuremath{\alpha}$ particles are distributed over a broad energy range in the vicinity and below the elastic scattering $^{6}\mathrm{He}$ peak. Energy integrated $\ensuremath{\alpha}$-particle cross sections have been obtained at ${\ensuremath{\theta}}_{\text{lab}}={36}^{\ensuremath{\circ}},{40}^{\ensuremath{\circ}}$, and ${60}^{\ensuremath{\circ}}$. The $\ensuremath{\alpha}$ energy distributions have been analyzed at a fixed laboratory angle $(\ensuremath{\approx}{60}^{\ensuremath{\circ}})$ in terms of the reaction $Q$ value, considering the $2n$-transfer reaction kinematics $^{120}\mathrm{Sn}(^{6}\mathrm{He},\ensuremath{\alpha})^{122}\mathrm{Sn}$. A kinematical analysis of the $Q$-value distribution shows that the recoil system $^{120}\mathrm{Sn}+2n$ is formed in highly excited states in the continuum, at increasing excitation energies as the bombarding energy increases. It is shown that by using Brink's formula, the excitation energy depends on the transferred angular momentum following a linear relation with the square of the angular momentum, indicating that some kind of dinuclear rotating system is formed after the reaction.

Characteristics and performance of a time of flight (TOF) spectrometer developed for performing fission mass distribution studies are presented. The spectrometer contains two TOF arms based on multi-wire proportional counters (MWPCs). Each arm has two MWPCs to form a start–stop detection system for TOF measurements. The start detector has an active area of 4 × 4 cm2. The stop detector is a two-dimensional position sensitive MWPC with an active area of 16 × 11 cm2. Salient features of the MWPCs are the use of reduced sub-millimeter wire pitches of 0.635 and 0.317 mm in the electrodes along with the use of gold plated tungsten wires of diameters 10 and 20 µm. A delay line for position electrodes is prepared using chip inductors and capacitors. Ten different configurations of MWPC were investigated for the start detector, which involved the use of three and four electrode geometries, use of different wire pitches, and use of aluminized mylar for timing electrodes. Performance results close to micro-channel plate detectors have been observed with some designs of MWPC, displaying rise times better than 2 ns with an estimated inherent time resolution of ∼100 ps FWHM. A position resolution of ∼1 mm (FWHM) has been observed. Design features of the MWPCs and their test performance results are described in this article.

A new method to obtain the nuclear radius from low energies total reaction cross section measurements is presented. Elastic scattering angular distributions of \(^6\)He on \(^9\)Be at two energies, namely, E\(_\mathrm {cm}= 9.72\) and 12.78 MeV, were analysed previously and the total reaction cross sections obtained are used to assess the \(^6\)He nuclear interaction radius. A comparison with the radius of the \(^6\)He obtained at higher energies is presented.

A description of the RIBRAS (radioactive ion beams in Brasil) facility is presented and the last experimental developments in the system are reported.

Fission fragment mass–angle and mass ratio distributions have been measured for the 30Si + 180Hf reaction in the beam energy range 128–148 MeV. Quasifission signature is observed in this reaction, forming the compound system 210Rn. The results are compared with a very asymmetric reaction 16O + 194Pt, forming the same compound nucleus. Calculations assuming saddle point, scission point and DNS models have been performed to interpret the experimental results. The results strongly suggest the entrance channel dependence of quasifission in heavy ion collisions.

Excitation functions of reaction residues produced in the $^{14}\mathrm{N}+^{169}\mathrm{Tm}$ system have been measured to high precision at energies above the fusion barrier, ranging from $1.04{V}_{B}$ to $1.30{V}_{B}$, and analyzed in the framework of the statistical model code pace4. Analysis of $\ensuremath{\alpha}$-emitting channels points toward the onset of incomplete fusion even at slightly above-barrier energies where complete fusion is supposed to be one of the dominant processes. The onset and strength of incomplete fusion have been deduced and studied in terms of various entrance channel parameters. Present results together with the reanalysis of existing data for various projectile-target combinations conclusively suggest strong influence of projectile structure on the onset of incomplete fusion. Also, a strong dependence on the Coulomb effect $({Z}_{P}{Z}_{T})$ has been observed for the present system along with different projectile-target combinations available in the literature. It is concluded that the fraction of incomplete fusion linearly increases with ${Z}_{P}{Z}_{T}$ and is found to be more for larger ${Z}_{P}{Z}_{T}$ values, indicating significantly important linear systematics.

Pre-equilibrium emissions affect the production of excited systems in nuclear reactions, thus modifying their properties which enter as input parameters in the comparison with statistical models. In this contribution, we discuss this subject referring to recent results from experiments performed at Legnaro National Laboratories (Italy) with the GARFIELD apparatus complemented with other detectors. ispartof: Acta Physica Polonica B vol:48 issue:3 pages:635-639 ispartof: location:Zakopane: POLAND status: published

An overview of the experiments performed at RIBRAS over the last year is presented. Elastic scattering and breakup reactions induced by light exotic projectiles on different targets have been measured and some results are presented here for the 120Sn(6He, α) reaction. Resonant scattering experiments have been performed with 10Be and 12C secondary beams on a CH2 thick target and the well known 12C+p resonance was identified. A gamma-particle experiment using a new system of LYSO scintillators to detect gammas was done.

In this work we present an elastic scattering angular distribution for the 8Li+58Ni system measured at Elab = 26.1 MeV. The 8Li beam was produced in the Radioactive Ion Beams in Brasil (RIBRAS) facility using the 7Li primary beam delivered by the 8-UD Pelletron accelerator. The angular distribution covers the angular range from 20 to 85 degrees in the center of mass frame. The data have been analysed by optical model and coupled channels calculations, including couplings to low-lying states in 8Li and the spin-orbit interaction. Our results indicate that the inclusion of the spin-orbit interaction in the calculations is important to describe the data at backward angles.

Multiple alpha coincidence and correlations are studied in the reaction $^{12}$C+$^{12}$C at 95 MeV for fusion-evaporation events completely detected in charge. Two specific channels with Carbon and Oxygen residues in coincidence with $\alpha$-particles are addressed, which are associated with anomalously high branching ratios with respect the predictions by Hauser-Feshbach calculations. Triple alpha emission appears kinematically compatible with a sequential emission from a highly excited Mg. The phase space distribution of $\alpha$-$\alpha$ coincidences suggests a correlated emission from a Mg compound, leaving an Oxygen residue excited above the threshold for neutron decay. These observations indicate a preferential $\alpha$ emission of $^{24}$Mg at excitation energies well above the threshold for $6-\alpha$ decay., Comment: 21 pages, 17 figures, second paper of a series of two

The correlations between mass distributions of the binary fragments, total kinetic energy (TKE), and neutron multiplicity have been investigated for the reaction $^{50}\text{Ti}+\phantom{\rule{0.16em}{0ex}}^{208}\text{Pb}$ at 294 MeV bombarding energy. Although this reaction has been used to synthesize the Rf ($Z=104$) superheavy element, a complete study of its fragmentation dynamics is still not available in the literature. In this work, average neutron multiplicities were extracted as a function of different fragment mass splits and TKE windows. A weak increase of the prescission neutron multiplicity is observed going from asymmetric to symmetric mass splits. A fission delay time of $4.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}$ s has been extracted for the symmetric fission. The neutron multiplicity extracted for the symmetric mass split was used to derive the average number of neutrons emitted in the spontaneous fission of $^{258}\text{Rf}$. The extrapolated value of $4.7\ifmmode\pm\else\textpm\fi{}1.4$ is found to be consistent with systematics of spontaneous and neutron-induced fission in heavy nuclei and with the results of previous works for superheavy nuclei with $Z=116$ and $Z=124$.

The $^{12}$C+$^{12}$C reaction at 95 MeV has been studied through the complete charge identification of its products by means of the GARFIELD+RCo experimental set-up at INFN Laboratori Nazionali di Legnaro (LNL). In this paper, the first of a series of two, a comparison to a dedicated Hauser-Feshbach calculation allows to select a set of dissipative events which corresponds, to a large extent, to the statistical evaporation of highly excited $^{24}$Mg. Information on the isotopic distribution of the evaporation residues in coincidence with their complete evaporation chain is also extracted. The set of data puts strong constraints on the behaviour of the level density of light nuclei above the threshold for particle emission. In particular, a fast increase of the level density parameter with excitation energy is supported by the data. Residual deviations from a statistical behaviour are seen in two specific channels, and tentatively associated with a contamination from direct reactions and/or $\alpha$-clustering effects. These channels are studied in further details in the second paper of the series., Comment: 24 pages, 15 figures, first paper of a series of two

Fission fragment angular distributions have been measured for 16O + 194Pt reaction forming the compound system 210Rn, in the laboratory energy range from 79 to 90 MeV. The measured fission fragment anisotropies as a function of E c . m . / V B are compared with the predictions of standard saddle point statistical model ( sspm ). Anisotropies calculated using the average excitation energy and angular momentum values could not reasonably fit the experimental data. Statistical model calculations were performed using the pace with modified fission barrier and level density parameters. Fission probability, evaporation residue cross section and neutron multiplicity were simultaneously used to fix the statistical parameters. Model calculations incorporating the chance nature of fission decay and scaled values of the rotating finite range model (RFRM) moment of inertia could reasonably fit the fragment angular anisotropies.

We have measured the elastic scattering cross-section for 8Li + 9Be and 8Li + 51V systems at 19.6MeV and 18.5MeV, respectively. We have also extracted total reaction cross sections from the elastic scattering analysis for several light weakly bound systems using the optical model with Woods-Saxon and double-folding-type potentials. Different reduction methods for the total reaction cross-sections have been applied to analyze and compare simultaneously all the systems.

The study of nuclear states built on clusters bound by valence neutrons in their molecular configurations is a field of large interest. Clustering becomes particularly important at the dripline, where weakly bound systems prevail. For light nuclei, at an excitation energy close to the particle separation value, there are experimental evidences of such structure effects, but this is still not the case for heavier nuclear systems. Several theoretical efforts have been done in the development of pre-formation alpha-clustering models, but there is still a lack of experimental data capable to give a direct feedback. The search of alpha-cluster evidences in medium-mass systems is therefore a new challenge which can give new hints in this field of research. In the past we have studied the reactions 250, 192 and 130 MeV O-16 + Sn-116, observing a significant increase in the fast emitted alpha-particle yield. This effect was ascribed to the presence of pre-formed alpha-clusters in the 16O projectile nucleus. To further investigate these aspects in a model independent way, a new experimental campaign has been performed with the GARFIELD + RCo set up. Two different reaction entrance channels (O-16 and F-19) at the same beam velocity (16AMeV) have been measured, leading to the same Rb-81* compound nucleus. In this contribution we report on the preliminary light-charged particles emission spectra obtained in coincidence with evaporation residues and their comparison with the results obtained from a Hybrid Exciton Model calculation.

Background: Detailed studies on the effect of the breakup of weakly bound projectile on fission are scarce. Distinguishing the events of compound nuclear (CN) fission from the breakup or transfer induced fission to understand the properties of measured fission fragments is difficult but desirable.Purpose: To investigate the effect of projectile breakup and its breakup threshold energy on fission-fragment (FF) mass distributions and folding angle distributions for $^{6,7}\mathrm{Li} + ^{238}\mathrm{U}$ reactions and find out the differences in the properties of the fission events produced by complete fusion (CF) from the total fusion (TF).Methods: The FF mass and folding angle distributions have been measured at energies around the Coulomb barrier using gas detectors by time-of-flight technique. The results are compared with the ones involving tightly bound projectiles as well as predictions from systematics to bring out the effect of the breakup.Results: A sharp increase in the peak to valley (P:V) ratio of FF mass distribution with the decrease in bombarding energy for $^{6,7}\mathrm{Li} + ^{238}\mathrm{U}$ reactions is observed when all events are assumed to be CN fission. As the beam energy falls through the fusion barrier, the full width half maximum (FWHM) of the FF folding angle distribution is found to increase at sub-barrier energies, unlike the reactions involving tightly bound projectiles where a linear decrease in FWHM is expected. By selecting pure CN events from the scatter plot of the velocity components of the composite nuclei, the energy dependence of the deduced FWHM is found to be consistent with the ones involving tightly bound projectiles. Similarly, the P:V ratio obtained for the selected CN events is consistent with the theoretical calculations as well as the experimental data for the proton induced reaction forming similar CN.Conclusions: The presence of projectile breakup induced fission and a relatively low breakup threshold for $^{6}\mathrm{Li}$ compared to $^{7}\mathrm{Li}$ explains the observed differences in the energy dependence of the P:V ratio and the FWHM of FF folding angle distributions for CF and TF fission in the present reactions.

The observation of $^{26}$Al gives us the proof of active nucleosynthesis in the Milky Way. However the identification of the main producers of $^{26}$Al is still a matter of debate. Many sites have been proposed, but our poor knowledge of the nuclear processes involved introduces high uncertainties. In particular, the limited accuracy on the $^{25}$Mg($\alpha$,n)$^{28}$Si reaction cross section has been identified as the main source of nuclear uncertainty in the production of $^{26}$Al in C/Ne explosive burning in massive stars, which has been suggested to be the main source of $^{26}$Al in the Galaxy. We studied this reaction through neutron spectroscopy at the CN Van de Graaff accelerator of the Legnaro National Laboratories. Thanks to this technique we are able to discriminate the ($\alpha$,n) events from possible contamination arising from parasitic reactions. In particular, we measured the neutron angular distributions at 5 different beam energies (between 3 and 5 MeV) in the \ang{17.5}-\ang{106} laboratory system angular range. The presented results disagree with the assumptions introduced in the analysis of a previous experiment., Comment: 9 pages, 9 figures - accepted by EPJA

Background: Several inclusive and few exclusive [evaporation residue (ER) gated] measurements for symmetric systems reported in the literature describe the anomalous deviations of light particle evaporation spectra from the statistical model predictions. However, no consistent description exists for these deviations.Purpose: To establish the consistent interpretation of reported anomalous deviations.Method: The inclusive and exclusive measurements of $\ensuremath{\alpha}$-particle, proton, and neutron spectra were carried out for the fusion of two relatively symmetric systems ${}^{28}$Si + ${}^{45}$Sc (E${}_{\mathrm{lab}}$ = 125 MeV and l${}_{\mathrm{max}}$ = 47$\ensuremath{\hbar}$) and ${}^{32}$S + ${}^{45}$Sc (E${}_{\mathrm{lab}}$ = 125 MeV and l${}_{\mathrm{max}}$ = 43$\ensuremath{\hbar}$) leading to the compound nuclei ${}^{73}$Br and ${}^{77}$Rb with excitation energies 78 MeV and 71 MeV, respectively.Results: The experimental light particle spectra for both the reactions show anomalous deviations from the statistical model predictions. The charged particles spectra are found to be suppressed, whereas the neutron spectra exhibit a bump at the higher energy tail. These spectra are investigated in terms of the modification of the important ingredients of the statistical model viz. the level density parameter, rescaling of the yrast line, and the use of $l$ value suggested by the dynamical models.Conclusions: It is conjectured that the higher partial waves do not fuse, but result in the formation of a deformed dinuclear system. The binding energy of neutrons is reduced while those for protons and $\ensuremath{\alpha}$ particles are enhanced in the deformed dinuclear system as compared to those in the shape-equilibrated system. Hence, the higher partial waves inhibit their contributions to the $\ensuremath{\alpha}$-particle spectra and lead to the preshape equilibrium of neutrons and protons, with the neutron emission dominating over the proton emission.

The detection of the 1809 keV emission line associated with the decay of 26 Al in the interstellar medium provides a direct evidence of recent nucleosynthesis events in our galaxy. 26 Al is thought to be mainly produced in massive stars, but in order to have a quantita- tive understanding of the 26 Al distribution, the cross section of all the nuclear reactions involved in its production should be accurately known. A recent sensitivity study demonstrated that the 25 Mg( ,n) 28 Si is the reaction with the strongest impact on the synthesis of 26 Al during explosive Neon and Carbon burning (4). In order to improve the experimental knowledge of the 25 Mg( ,n) 28 Si cross section, a new direct measurement has been performed at Legnaro National Laboratories. The experimental setup, the data analysis and preliminary results are discussed.

The lifetimes of high spin states of 75 Kr have been determined via 50 Cr ( 28 Si, 2pn) 75 Kr reaction in positive parity band using the Doppler-shift attenuation method. The transition quadrupole moments Q t deduced from lifetime measurements have been compared with 75 Br. Experimental results obtained from lifetime measurement are interpreted in the framework of projected shell model.

Complete fusion cross sections for ${}^{7}$Li+${}^{144,152}$Sm reactions have been measured at energies around the Coulomb barrier by offline $\ensuremath{\gamma}$-counting technique. Measured cross sections for the above two reactions are found to be similar at energies well above the Coulomb barrier, however, at sub-barrier energies the cross sections for the ${}^{7}$Li+${}^{152}$Sm system are much higher compared to the ${}^{7}$Li+${}^{144}$Sm system, manifesting the effect of target deformation. Cross sections for the present reactions at above-barrier energies are found to be larger than previously measured reactions involving ${}^{6}$Li projectile with the same targets, possibly due to smaller breakup probability of ${}^{7}$Li than ${}^{6}$Li. Coupled-channels calculations show that the experimental fusion cross sections for both the systems are enhanced at subbarrier energies and suppressed at above-barrier energies compared to the respective one-dimensional barrier penetration model predictions. The calculations by different models show that the measured complete fusion cross sections at above-barrier energies are suppressed up to $\ensuremath{\sim}$25% compared to the theoretical predictions. It also reveals that a large part of the suppression could be due to inelastic and transfer coupling.

High spin states of ${}^{109}$In were investigated using the reaction ${}^{96}$Zr(${}^{19}$F, 6n)${}^{109}$In at a beam energy of 105 MeV. New level sequences have been found in this nucleus. In an earlier known band, the ordering of some of the transitions have been changed and assigned a three-quasiparticle $\ensuremath{\pi}$(g${}_{9/2}$)${}^{\ensuremath{-}1}$ $\ensuremath{\bigotimes}$ $\ensuremath{\nu}$[h${}_{11/2}$(d${}_{5/2}$/g${}_{7/2}$)] configuration. Similar three-quasiparticle bands have also been found earlier in lighter mass ${}^{105}$In and ${}^{107}$In nuclei. Systematics of these bands in ${}^{105}$In, ${}^{107}$In, and ${}^{109}$In nuclei are discussed in the present work within the framework of the tilted axis cranking model.

Elastic scattering angular distributions using the weakly bound projectile 7Li on medium-mass target 116Sn were measured for 10 different beam energies from much below to above the Coulomb barrier. Optical model (OM) analysis was carried out using the famous double folding Sao Paulo Potential (SPP) to investigate the energy dependence of the interacting polarizing potentials. The absence of the usual Threshold Anomaly (TA) is observed. Thus this unusual behavior of the interacting potentials indicates the coupling of the breakup channels with the elastic ones.

Elastic-scattering angular distributions of 7Li on 116Sn have been measured at different bombarding energies between 18 to 35 MeV. The effects of the weakly bound projectile breakup channel on the bombarding energy dependence of the interaction potential have been investigated. In this work we present the experimental results, along with the theoretical analysis using Woods-Saxon potential to investigate the energy dependence of the interacting polarizing potentials. Total reaction cross-sections are also presented and discussed.

Fission fragment angular distributions have been measured for a $^{9}\mathrm{Be}$ $+$ $^{232}\mathrm{Th}$ system at four different beam energies around the Coulomb barrier. The experimental results on fission fragment anisotropies have been compared with predictions of the standard statistical saddle-point model (SSPM) and the preequilibrium fission (PEQ) model including projectile ground-state spin. It is observed that both SSPM and the PEQ model fail to reproduce the experimental results, indicating that projectile breakup may affect the fission fragment anisotropies.

The fission fragment mass angle correlations and mass ratio distributions have been investigated for the two systems $^{16}\mathrm{O}+^{197}\mathrm{Au}$ and $^{27}\mathrm{Al}+^{186}\mathrm{W}$, leading to the same compound nucleus $^{213}\mathrm{Fr}$ around the Coulomb barrier energies. Systematic analysis of the variance of the mass distributions as a function of temperature and angular momentum suggests true compound nuclear fission for both the reactions, indicating the absence of nonequilibrium fission processes.

Excited states of ${}_{56}^{135}{\mathrm{Ba}}_{79}$ at high spins are studied using the reaction $^{130}\mathrm{Te}$($^{9}\mathrm{Be}$,$4n$)${}_{56}^{135}{\mathrm{Ba}}_{79}$ at $42.5$-MeV beam energy. The earlier known level scheme is extended up to $6.4$-MeV excitation energy and ($37/2$)$\ensuremath{\hbar}$ spin with the addition of several transitions. We have performed polarization asymmetry measurements for some of the strong transitions by using a Clover detector to assign the parity. A comparison of experimental data with the results of tilted axis cranking calculations based on various configurations indicates the coexistence of multiple minima in the triaxial deformation ($\ensuremath{\gamma}$), whereas axial symmetric deformation (${\ensuremath{\epsilon}}_{2}$) remains constant around $0.09$.

High spin states of $^{107}\mathrm{In}$ have been investigated using the reaction $^{94}\mathrm{Mo}$($^{16}\mathrm{O}$,$p2n$)$^{107}\mathrm{In}$ at a beam energy of $70$ MeV. A total of $62$ new $\ensuremath{\gamma}$ transitions have been placed in the level scheme and several $\ensuremath{\Delta}I=1$ sequences and one $\ensuremath{\Delta}I=2$ sequence have been found. Lifetime measurements using the Doppler-shift attenuation method (DSAM) have been carried out for band states of $\ensuremath{\Delta}I=1$ and $\ensuremath{\Delta}I=2$. A decreasing trend of $B(M1)$ strengths with increasing spin deduced for the $\ensuremath{\Delta}I=1$ band indicates the presence of a shears mechanism. The experimental data for this band are compared with the tilted axis cranking (TAC) calculations. The $\ensuremath{\Delta}I=2$ band has been found to be a deformed band with ${\ensuremath{\beta}}_{2}~0.2$.

Fission fragment mass ratio distributions have been measured for the reactions $^{16}\mathrm{O}+^{194}\mathrm{Pt}$ and $^{24}\mathrm{Mg}+^{186}\mathrm{W}$, both leading to the same compound nucleus, $^{210}\mathrm{Rn}$, at near-barrier energies. The measured fission fragment mass ratio variances for $^{16}\mathrm{O}+^{194}\mathrm{Pt}$ and $^{24}\mathrm{Mg}+^{186}\mathrm{W}$ are compared with the calculations assuming compound nucleus formation. Mass variances of fragments from the $^{24}\mathrm{Mg}+^{186}\mathrm{W}$ reaction show a dramatic deviation from the compound nucleus behavior. This suggests strong evidence for onset of the quasifission process in this reaction.