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The fragment emission mechanism in the binary decay of composites formed in the reactions $^{20}\mathrm{Ne}+^{56}\mathrm{Fe}$ and $^{16}\mathrm{O}+^{58}\mathrm{Ni}$ has been studied at two different excitation energies. The inclusive energy and angular distributions of the emitted fragments $^{6,7}\text{Li}$, $^{7,8,9}\text{Be}$, $^{10,11}\text{B}$, and $^{11,12,13,14}\text{C}$ have been measured in the laboratory angles ranging from ${15}^{\ensuremath{\circ}}$ to ${35}^{\ensuremath{\circ}}$ (corresponding angles in center of mass ranging from ${20}^{\ensuremath{\circ}}$ to ${50}^{\ensuremath{\circ}}$). The energy distributions of the fragments are found to be Gaussian and peaked at energies higher than those expected from fusion-fission-type reactions. The center-of-mass angular distributions of all the fragments have been found to fall faster than $\ensuremath{\approx}1/\mathrm{sin}{\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}$-like dependence and the average $Q$ values of the fragments are found to decrease with increasing the center-of-mass angle of the emitted fragment for both the systems. The above characteristics of fragments signify that they were emitted from nonequilibrium sources, produced in a highly energy damped deep-inelastic-type reaction. The lifetimes of the dinuclear composites estimated from the angular distributions of these fragments are found to be in the range of $\ensuremath{\approx}(0.5--2.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}$ s, which are smaller than the respective compound-nuclear lifetimes $[\ensuremath{\approx}(1.0--2.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}21} \mathrm{s}]$. The angular-momentum dissipations estimated from the average kinetic energies of the fragments are found to be, for lighter fragments in particular, greater than those predicted by the empirical sticking limit.

High and medium spin structures of 130,131Xe have been studied using α-induced fusion-evaporation reaction and the Indian National Gamma Array (INGA) coupled with a digital data acquisition system. Various new band structures and near yrast levels of 131Xe have been established. The multipolarities of the observed transitions have been assigned on the basis of the DCO ratios and the polarization asymmetry measurements. Band structures based on 1-quasi-particle (qp), 3-qp configurations have been observed. A new Magnetic Rotational (MR) band based on 5-qp configuration has also been established in 131Xe. The MR band has been interpreted in terms of shears mechanism with principal axis cranking (SPAC) calculations. Shell Model calculations are carried out to describe the non yrast states of 131Xe above the 11/2− isomer. New excited states have also been identified in 130Xe, produced in the same reaction.

The cyclotron at Variable Energy Cyclotron Centre (VECC), Kolkata, has recentlyrecently completed its 40 years of operation in 2017. During the past four decades, VECC has been able to cross several milestones in exploring the properties of nuclei with the help of low energy light as well as heavy ions accelerated by the cyclotron. In this review, we endeavour to present an overall picture of the intense research activities in various branches of nuclear physics carried out in the past four decades using cyclotron, with special emphasis on the important achievements in each field.

Background: The influence of shell effect on the dynamics of the fusion fission process and its evolution with excitation energy in the preactinide Hg-Pb region in general is a matter of intense research in recent years. In particular, a strong ambiguity remains for the neutron shell closed $^{210}\mathrm{Po}$ nucleus regarding the role of shell effect in fission around $\ensuremath{\approx}30--40\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ of excitation energy.Purpose: We have measured the fission fragment mass distribution of $^{210}\mathrm{Po}$ populated using fusion of $^{4}\mathrm{He}+^{206}\mathrm{Pb}$ at different excitation energies and compare the result with recent theoretical predictions as well as with our previous measurement for the same nucleus populated through a different entrance channel. Mass distribution in the fission of the neighboring nuclei $^{213}\mathrm{At}$ is also studied for comparison.Methods: Two large area multiwire proportional counters (MWPC) were used for complete kinematical measurement of the coincident fission fragments. The time of flight differences of the coincident fission fragments were used to directly extract the fission fragment mass distributions.Results: The measured fragment mass distribution for the reactions $^{4}\mathrm{He}+^{206}\mathrm{Pb}$ and $^{4}\mathrm{He}+^{209}\mathrm{Bi}$ were symmetric and the width of the mass distributions were found to increase monotonically with excitation energy above 36.7 MeV and 32.9 MeV, respectively, indicating the absence of shell effects at the saddle. However, in the fission of $^{210}\mathrm{Po}$, we find minor deviation from symmetric mass distributions at the lowest excitation energy (30.8 MeV).Conclusion: Persistence of shell effect in fission fragment mass distribution of $^{210}\mathrm{Po}$ was observed at the excitation energy $\ensuremath{\approx}31\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ as predicted by the theory; at higher excitation energy, however, the present study reaffirms the absence of any shell correction in the fission of $^{210}\mathrm{Po}$.

The fission fragment mass distributions have been measured in the reactions 16O + 184W and 19F+ 181Ta populating the same compound nucleus 200Pb? at similar excitation energies. It is found that the widths of the mass distribution increases monotonically with excitation energy, indicating the absence of quasi-fission for both reactions. This is contrary to two recent claims of the presence of quasi-fission in the above mentioned reactions., Comment: Accepted for publication as a regular article in Physical Review C

The reaction [Formula: see text]Al([Formula: see text],3He) at 25 MeV beam energy has been utilized to study the states in even–even nucleus [Formula: see text]Mg. The spectroscopic factors have been extracted for the states of [Formula: see text]Mg up to 7.50[Formula: see text]MeV excitation energy using local, zero-range distorted wave Born approximation. The extracted spectroscopic factors have been compared with the previously reported values. The present results were also compared with the predictions from a theoretical shell model and rotational model.

The inclusive energy distributions of the complex fragments (3{

The inclusive energy distributions of fragments with Z $\ensuremath{\ge}$ 3 emitted from the bombardment of $^{12}\mathrm{C}$ by $^{20}\mathrm{Ne}$ beams with incident energies between 145 and 200 MeV have been measured in the angular range ${\ensuremath{\theta}}_{\mathrm{lab}}~{10}^{\ifmmode^\circ\else\textdegree\fi{}}\text{\ensuremath{-}}{50}^{\ifmmode^\circ\else\textdegree\fi{}}$. Damped fragment yields in all cases have been found to be characteristic of emission from fully energy equilibrated composites; for B and C fragments, average Q values, $\ensuremath{\langle}Q\ensuremath{\rangle}$, were independent of the center-of-mass emission angle (${\ensuremath{\theta}}_{\mathrm{c.m}.}$), and the angular distributions followed a $~1/\mathrm{sin}{\ensuremath{\theta}}_{\mathrm{c.m}.}$-like variation, signifying long lifetimes of the emitting dinuclear systems. Estimates of total yields of these fragments have been found to be much larger than those predicted by the standard statistical model. This may be indicative of the survival of an orbiting-like process in the $^{12}\mathrm{C}+^{20}\mathrm{Ne}$ system at these energies.