In the present work, experimental study of incomplete fusion in the 19F + 93Nb system has been carried out in the energy range of approximate to 3-6 MeV/nucleon. The off-line gamma -ray spectrometry was used to measure the cross sections of evaporation residues populated in this system. The analyses of experimentally measured excitation functions have been performed with theoretical predictions from the statistical model code PACE4 to probe the associated reaction mechanism. The imitation of xn/pxn channels data grossly by the statistical model confirms the production of these residues via complete fusion process. However, the noticeable enhancement observation in alpha-channel cross sections hints at the signatures of breakup fusion in addition to the dominant complete fusion. Furthermore, the present study, in light of literature data involving the interaction of 13C, 16O, and 18O projectiles with the same target 93Nb, imparts the reliance of projectile structure on incomplete fusion, and the results may be understood on the basis of the projectile Q alpha value. An attempt has also been made to discuss the trend of incomplete fusion fraction through the Coulomb factor and total asymmetry of the interacting partners. For the present studied system, the fusion function calculated from the experimentally measured fusion cross section data is compared with the universal fusion function to get information about fusion supression.

An outstanding problem in the heavy-ion (HI)-induced nuclear reactions is understanding the role of incomplete fusion (ICF) and its dependence on various entrance channel parameters relatively at energies slightly above the Coulomb barrier. For this purpose, the excitation functions (EFs) of reaction residues populated in ^14 N+ ^51 V system have been measured at energies ≈ 3–6 MeV/nucleon. The stacked foil activation technique followed by an off-line γ -ray spectrometer with a high-resolution HPGe detector has been employed. The measured excitation functions are compared with the theoretical predictions, obtained from statistical model codes PACE4 and ALICE-91. The analysis of the present work suggests that the experimental excitation functions for xn and/or pxn channels are grossly reproduced by the theoretical predictions. However, for α -emitting-channels, the measured EFs are found to be underestimated by the statistical predictions which may be attributed to the breakup fusion of the projectile with the target nucleus. For a better understanding of ICF reaction dynamics, the percentage of ICF fraction has been deduced. The present study in light of the literature data provides insight into the dependence of ICF processes on the projectile structure. Further, some physical parameters such as mass asymmetry of interacting partners, Coulomb interaction between projectile and target ( Z_P Z_T ), and the target deformation parameter ( β _2 ) are also found liable for projectile breakup prior to fusion.

The level structure of the transitional nucleus $\mathrm{^{217}Ra}$ has been extended with the addition of around 20 new transitions. The discrepancies between the placements of several transitions reported in the earlier studies are resolved. The newly-established negative-parity sequence at low excitation energies hints at the expected parity-doublet structures in this nucleus. The properties of the observed simplex bands are compared with that of similar bands in neighboring nuclei. Since the presence of parity-doublet structures reflect octupole correlations, theoretical calculations using reflection-asymmetric triaxial particle rotor model (RAT-PRM) have been performed. A comparison of the observed features of the simplex bands with the predictions of the RAT-PRM calculations suggests that $\mathrm{^{217}Ra}$ exhibits an intermediate the behavior between the extremes of spherical and octupole-deformed nuclei. The termination of the simplex bands at intermediate energies and the structures lying above reflect the dominance of the single-particle excitations at higher excitation energies.

Yrast and near-yrast states above the known 25/2$^{+}$ isomer in $^{207}$At are established for the first time. The level scheme is extended up to 47/2$\hbar$ and 6.5 MeV with the addition of about 60 new $\gamma$-ray transitions. The half-life of the 25/2$^{+}$ isomer is revisited and a value of $T_{1/2}$ = 107.5(9) ns is deduced. Evidence of a hitherto unobserved 29/2$^{+}$ isomer in $^{207}$At is presented. A systematic study of $B(E3)$ values for the transitions de-exciting the 29/2$^{+}$ isomer in the neighboring odd-$A$ At isotopes suggests a half-life in the 2$-$4.5 $\mu$s range for this state in $^{207}$At. The experimental results are compared with large-scale shell-model calculations performed using the KHM3Y effective interaction in the $Z$ = 50$-$126, $N$ = 82$-$184 model space and an overall good agreement is noted between the theory and the experiment. A qualitative comparison of the excited states and the isomers with analogous states in neighboring nuclei provides further insight into the structure of $^{207}$At.

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 N-14 + Tm-169 at energy approximate to 5.9 MeV/nucleon. A stack target-catcher activation technique followed by offline-gamma-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 ( alpha )-value of projectile, mass-asymmetry (mu (MA)), and Coulomb factor (Z (P) Z (T)), it has been found that the Q ( alpha )-value systematic for N-14 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 (zeta) for the first time in ICF reactions to see the combined effect of mass-asymmetry (mu (MA)) and Z (P) Z (T), as this parameter is better suited than mu (MA) and Z (P) Z (T) individually and has a linear dependency on F (ICF)(%).

We report measured cross-section data of the residues produced in the C-13-induced reaction on Nb-93 within the 63.7-87.1-MeV energy range. The off-line gamma-ray spectroscopy method has been used to measure the cross sections of the radionuclides produced in this system. The analysis of present measured cross-section data has been carried out within the light of well-established statistical model code PACE4. The excitation function of residues populated via xn and/or pxn channels are found to be in fair agreement with those estimated by the theoretical model code, which confirms the assembly of these residues via complete fusion process. A considerable enhancement in the measured cross-section data has been observed for the residues involving alpha-emitting channels as compared to the theoretical predictions. The observed enhancement in the cross sections has been assigned to the incomplete fusion processes. Furthermore, in order to have a better insight into the onset and strength of incomplete fusion, termed as the incomplete fusion fraction has been deduced for the present paper and is compared with O-16 and O-18 beams on the same target Nb-93. This suggests that the incomplete fusion fraction is strongly influenced by the entrance channel, which may be understood in terms of the projectile Q(alpha) value. The comparison of this paper with literature data also shows that the incomplete fusion probability increases with various entrance channel parameters, such as projectile structure, projectile energy, and mass asymmetry of interacting partners.

We report measured cross-section data of the residues produced in the $^{13}\mathrm{C}$-induced reaction on $^{93}\mathrm{Nb}$ within the 63.7--87.1-MeV energy range. The off-line $\ensuremath{\gamma}$-ray spectroscopy method has been used to measure the cross sections of the radionuclides produced in this system. The analysis of present measured cross-section data has been carried out within the light of well-established statistical model code pace4. The excitation function of residues populated via $xn$ and/or $pxn$ channels are found to be in fair agreement with those estimated by the theoretical model code, which confirms the assembly of these residues via complete fusion process. A considerable enhancement in the measured cross-section data has been observed for the residues involving $\ensuremath{\alpha}$-emitting channels as compared to the theoretical predictions. The observed enhancement in the cross sections has been assigned to the incomplete fusion processes. Furthermore, in order to have a better insight into the onset and strength of incomplete fusion, termed as the incomplete fusion fraction has been deduced for the present paper and is compared with $^{16}\mathrm{O}$ and $^{18}\mathrm{O}$ beams on the same target $^{93}\mathrm{Nb}$. This suggests that the incomplete fusion fraction is strongly influenced by the entrance channel, which may be understood in terms of the projectile ${Q}_{\ensuremath{\alpha}}$ value. The comparison of this paper with literature data also shows that the incomplete fusion probability increases with various entrance channel parameters, such as projectile structure, projectile energy, and mass asymmetry of interacting partners.

The incomplete fusion dynamics in the $^{18}\mathrm{O}+^{93}\mathrm{Nb}$ system at energies above the Coulomb barrier has been investigated. The experimentally measured cross sections have been compared with the theoretical predictions of the statistical model code pace4. To examine the effect of entrance channel parameters on the onset and strength of incomplete fusion, relative contributions of complete and incomplete fusion have been deduced from the analysis of measured excitation functions. The contribution of incomplete fusion deduced from the analysis of excitation functions has been studied in terms of various entrance channel parameters, namely, entrance channel mass asymmetry (${\ensuremath{\mu}}_{A}$) of interacting projectile and target combination, Coulomb factor (${Z}_{P}{Z}_{T}$), ground state $\ensuremath{\alpha}\text{\ensuremath{-}}Q$ value of the reaction, and neutron skin thickness of target nuclei. It has been found that the probability of incomplete fusion depends strongly on entrance channel parameters. Further, the incomplete fusion contribution for the $^{18}\mathrm{O}$ projectile with two excess neutrons is noticed to be relatively larger as compared to $^{16}\mathrm{O}$. This may be due to the larger probability of breakup for the $^{18}\mathrm{O}$ projectile resulting in rather weak binding forces as compared to $^{16}\mathrm{O}$. The existence of incomplete fusion below critical angular momentum (${\ensuremath{\ell}}_{\mathrm{crit}}$), i.e., $\ensuremath{\ell}\ensuremath{\leqslant}\phantom{\rule{4pt}{0ex}}{\ensuremath{\ell}}_{\mathrm{crit}}$, has also been observed for the studied system.

Sunil Dutt, M Saxena, P J Napiorkowski, R Kumar, T Abrahahm, J M Allmond, A Gwalik, K Hadynska-Klęk, M Hlebowicz, J Iwanicki, M Kisieliński, M Komorowska, M Kowalczyk, T Marchlewski, M Matejska-Minda, F Oleszczuk, M Palacz, W Piątek, L Próchniak, I A Rizvi, J Samorajczyk, J Srebrny, A Tucholski, W Wróblewski & K Wrzosek-Lipska aDepartment of Physics, Aligarh Muslim University, Aligarh 202 001, India bHeavy Ion Laboratory, University of Warsaw, Warsaw 05077, Poland cInter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067, India dOak Ridge National Laboratory, Oak Ridge 37830, USA eFaculty of Physics, and Applied Computer Science, University of Łodź, Łodź, Poland fWarsaw University of Technology, Warszawa 00661, Poland gNational Centre for Nuclear Research, Świerk 05400, Poland hFaculty of Physics, University of Warsaw, Warsaw 02093, Poland iThe H. Niewodniczański Institute of Nuclear Physics PAN Kraków, Kraków 31342, Poland

To accomplish a systematic study of incomplete fusion, verification of more experimental data of different projectile-target combinations is required. For this purpose, the excitation functions for several evaporation residues formed in $^{16}\mathrm{O}+^{51}\mathrm{V}$ interaction at energy $\ensuremath{\approx}4$--7 MeV/$A$ were measured. The experimentally measured excitation functions were compared with the theoretical predictions obtained from statistical model code alice-91. The measured excitation functions for $xn$ and/or $pxn$ channels are found to be in good agreement with theoretical predictions. However, a significant enhancement has been observed for $\ensuremath{\alpha}$-breakup fusion modes. This enhancement in the cross section gives clear indication of incomplete fusion of the projectile with the target. To gain insightin to the reaction dynamics, incomplete fusion probability has been deduced. This shows that the incomplete fusion process gradually increases in importance with increasing incident energy. The present results have also been compared with the results obtained in the interaction of $^{12}\mathrm{C}$ and $^{20}\mathrm{Ne}$ with $^{51}\mathrm{V}$ where a strong projectile structure effect has been observed, which can be explained in terms of the $\ensuremath{\alpha}$-decay $Q$ value of the projectile. It is also observed that the probability of breakup of a projectile prior to fusion depends on mass asymmetry of the interacting partners as well as on the deformation of the target nucleus.

To correlate the single particle and collective behaviour of the nuclei, some of the isotopic chains in the vicinity of doubly magic Sn and Pb-cores have been studied with the most recent data available. Energy ratios E (6(1)(+))/E(4(1)(+)) and E(4(1)(+))/E(2(1)(+)) have been calculated to predict the nature of the studied isotopes. The energy space has been divided into four regimes, classifying the single particle, collective, and two forbidden regions. Signature of coexisting structures (collective and non-collective) arising out of intruder configurations in the yrast excitation has also been interpreted. Recently observed neutron rich Sn-130 to Sn-138, and Pb-210 to Pb-216 isotopes have also been included in the present study.

Department of Physics, Aligarh Muslim University, Aligarh (U. P.)-202 002, INDIA Department of Physics, Maulana Azad National Urdu University, Darbhanga (Bihar)-846 001, INDIA Department of Physics, Bareilly College, Bareilly (U. P.)-243 005, INDIA NP-Group, Inter University Accelerator Centre, New Delhi-110 067, INDIA Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia . * muntazirgull1@gmail.com

Incomplete fusion (ICF) has conspicuous importance in the study of heavy ion (HI) induced reaction. The recent study [1-6] shows the significant contribution of ICF at projectile energies near the Coulomb barrier where complete fusion (CF) is assume to be the sole contributor to the total reaction cross-section. It has been observed that at projectile energy near the Coulomb barrier, both the complete fusion (CF) and incomplete fusion (ICF) may be considered as dominant reaction mechanisms. The incomplete fusion (ICF) reactions are quite specific due to complex nature of incomplete mass transfer and its dependence on various entrance channel parameters like type of projectile, energy of projectile, transfer of input angular momentum (l), deformations of the interacting nuclides, mass-asymmetry and αbreak up energy (Qα). These reactions provide very detailed information for the studies on nuclear structure as well as nuclear dynamics. At low projectile energies (3-7 MeV/A), the influence of the projectile breakup on fusion is not yet well understood and also in most of the recent studies -cluster structure beams have been used. Thus the present study is motivated to study the effect of projectile structure on incomplete fusion at low bombarding energies for neutron rich projectile also. In extension to our earlier work [5], the present paper deals with the study of dependence of ICF entrance channel parameters and the comparison of probability of incomplete fusion (FICF(%) or ICF(%)) of the present system with the other systems of same target but different projectile have been presented and discussed.

In the present work, production cross-sections for several fission like events after complete fusion (CF) and/or incomplete (ICF) in 16 O+ 175 Lu system at ≈ 5.5 MeV/A and 6.25 MeV/A have been measured to study mass and charge distributions.The well established activation technique was used for the present measurements.Moreover, isotopic yield distributions have also been studied using experimentally measured production cross-sections of few isotopes like Yttrium (Y) and Indium (In) which have been found to be symmetric as expected.Analysis of the data indicates that the nuclear fission is one of the dominating decay modes of heavy nuclei expected to be populated via complete and/or incomplete fusion at incident 16 O energies 5.5 and 6.25 MeV/A, where the evaporation of light nuclear particles are most likely to be expected.The statistical analysis of the isotopic yield distribution has also been carried out and the most probable values of mass and charge of fission like products were determined for the present system.

In this paper, we have made an attempt to measure the excitation functions for the evaporation residues identified in the interaction of 16O+55Mn system with a view to study the complete and incomplete fusion reaction dynamics in heavy ion induced reactions. The motivation of this experiment is to study the breakup of 16O in reactions below 7 MeV/A and to compare the excitation functions for 12C, 16O and 20Ne induced reactions with different targets leading to the same composite system (71As in this case). PACE-4 and ALICE-91 have been used for the analysis with the same set of input parameters as those adopted in the case of 12C+59Co and 20Ne+51V systems. The measured excitation functions for a particular decay channel in the three cases (i.e. 12C+59Co, 16O+55Mn and 20Ne+51V) have been compared and found to obey Bohr′s assumption in case of complete fusion channels. The effects of Coulomb barrier and other entrance channel parameters are found to be quite significant in determining the decay mode of the composite system. Further the incomplete fusion dynamics is also observed to be of considerable importance in the present energy region.

The excitation functions for 59Co(12C,pn)69Ge, 59Co(12C,2pn)68Ga, 59Co(12C,p4n)68Ge, 59Co(12C,αp4n)62Zn reactions for 12C+59Co projectile-target system have been measured for the first time. The recoil catcher technique followed by off-line γ-ray spectroscopy with HPGe detectors was used. The measured excitation functions are compared with the calculations based on the available tatistical model codes. The probability of incomplete fusion is found to increase with the projectile energy. Moreover, an attempt has been made to observe the impact of mass-asymmetry on incomplete fusion probability. The effect of α-break-up energy (Qα) on the ICF probability is also studied with the available data.

Sabir Ali1,∗ Tauseef Ahmad, Kamal Kumar, I. A. Rizvi, Sunil Dutt, Avinash Agarwal, S. S. Ghugre, A. K. Sinha, and A. K. Chaubey 4 Department of Physics, Aligarh Muslim University, Aligarh 202002, INDIA Department of Physics, Bareilly College, Bareilly 243005, INDIA UGC-DAE Consortium for Scientific Research, Kolkata 700098, INDIA and Department of Physics, Addis Ababa University, Adis Ababa 1176, ETHIOPIA

In recent years the unexpected influence of incomplete fusion over total fusion cross-section has been observed at projectile energy as low as 4-7 MeV/A [1]. The complex nature of incomplete mass transfer and its ambiguous dependence on various entrance channel parameters like projectile type, energy, imparted angular momentum (l) to the system, Qα-value, mass asymmetry of the interaction partners, etc. has renewed the interest among nuclear physicists to probe the exact dynamics of incomplete fusion. Parker et al. [2] observed forward α-particles in low Zheavy ion interactions on 51 V target at energies ≈ 6 MeV/A. Morgenstern et al.[3] studied the velocity spectra of evaporation residues and also showed that, incomplete fusion reactions significantly contributes to total reaction cross section for mass asymmetric systems as compared to mass symmetric systems at the same relative velocity. Later on, studies by Vineyard et al.[4] and Chakrabarty et al.[5] also supported the findings of Morgenstern et al. [3,4]. In the present work, to explore the dynamics of incomplete fusion fraction (%FICF) with mass-asymmetry [AT/(AT+AP)], we have studied incomplete fusion fractions of different projectile-target combinations. The variation of %FICF with the normalized projectile energy is also studied. The percentage fraction of incomplete fusion (%FICF) for the 16 O+ 45 Sc and 12 C+ 59 Co systems has been calculated as suggested in Ref.[1] and rest of the data is taken from the respective references as given in Fig 1. The value of FICF, which is a measure of relative strength of incomplete fusion to the total fusion, is calculated by using the formula, defined as (%)FICF =(ΣσICF/σTF)×100, and is plotted as a function of normalized projectile energy (EProj/VB ; where VB is fusion barrier) along with several other systems available in the literature, and is shown in Fig. 1. It is clear from figure that the value of FICF increases invariably with the projectile energy (as the probability of the breakup of incident projectile into α-clusters also increases with the increasing energy) and establish it as an important tool to probe ICF.