PHYSICAL REVIEW C 95, 064603 (2017) Fragment emission mechanism in the 32 S + 12 C reaction Ratnesh Pandey, 1 , * S. Kundu, 1, 2 C. Bhattacharya, 1, 2 K. Banerjee, 1, 2 T. K. Rana, 1 S. Manna, 1, 2 G. Mukherjee, 1, 2 J. K. Meena, 1 A. Chaudhuri, 1, 2 T. Roy, 1, 2 Pratap Roy, 1, 2 Md. A. Asgar, 1, 2 V. Srivastava, 1 A. Dey, 1 M. Sinha, 1 T. K. Ghosh, 1, 2 S. Bhattacharya, 1 S. K. Pandit, 2, 3 K. Mahata, 2, 3 P. Patle, 3 S. Pal, 4 A. Shrivastava, 2, 3 and V. Nanal 4 1 Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata - 700064, India 2 Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai - 400094, India 3 Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India 4 Tata Institute of Fundamental Research, Mumbai - 400005, India (Received 25 April 2017; published 5 June 2017) The complex fragment emission from the decay of fully energy-relaxed composite, 44 Ti ∗ formed via the 32 S + 12 C reaction at two excitation energies, have been studied. Inclusive energy distributions of the fragments (3  Z  8) emitted in the reaction 32 S + 12 C have been measured in the angular range ∼16 ◦ –28 ◦ , at two incident energies, 200 and 220 MeV, respectively. Damped fragment yields in all the cases have been found to have the characteristic of emission from fully-energy-equilibrated composites. The binary fragment yields are found to be in good agreement with the standard statistical model predictions of the extended Hauser–Feshbach model (EHFM). DOI: 10.1103/PhysRevC.95.064603 I. INTRODUCTION For the last few decades, extensive studies [1–11] have been made to understand the fragment emission mechanisms for low-energy nucleus-nucleus collisions. These studies reveal that, for low energy (10 MeV/u), light heavy-ion (A proj + A target  60) collisions, fusion followed by asymmetric fission (FF) [12–17] and deep inelastic orbiting [8–11] are two dominant mechanisms, which contribute to the observed fully energy damped yields of the fragments. It has been observed that deep inelastic orbiting mechanism [8–11] plays a signifi- cant role in fragment emission from the reactions involving α-cluster nuclei (e.g., 20 Ne + 12 C[8,9], 24 Mg + 12 C[18], 28 Si + 12 C[19], etc.). In the deep inelastic orbiting process it is assumed that, instead of forming a compound nucleus (CN) as in FF process, a long-lived, dinuclear molecular complex [11] is formed with a strong memory of the entrance channel. In addition, in the case of the light heavy-ion systems, the shapes of the orbiting dinuclear systems are quite similar to the saddle and scission shapes obtained in the course of evolution of the FF process. Moreover, both orbiting and fusion-fission processes occur on similar timescales and hence the distinction between the signatures of the two processes is a real challenge. In spite of this, quite a few attempts have been made to differentiate these processes. In extensive studies for 20 Ne + 12 C[20,21], 16 O + 12 C[22] systems, it has been demonstrated that, even at higher bombarding energies, the signatures of equilibration persists, i.e., the most probable Q values for the fragments were found to be independent of detection angles and the resulting angular distributions of the fragments were found to have ∼1/sinθ c.m. -like angular dependence; However, the enhancement in the fully energy damped fragment yields near the entrance channel over the statistical model predictions, indicated the survival of orbiting at higher excitation energies. Since it is believed that orbiting is * ratnesh@vecc.gov.in associated with the formation of a highly deformed dinuclear configuration, the study of deformation of the hot composites using light charged particle (LCP) emission as a probe [23] can be used to differentiate between FF and orbiting processes. Survival of orbiting has further been established for the 20 Ne + 12 C[24], 16 O + 12 C[25], 28 Si + 12 C[26] systems, where large deformations have been observed over the statistical model predictions by using LCP as a probe. So it will be interesting to investigate if orbiting continues to play significant role in heavier α-cluster nuclei, too. In a detailed study of fragment emission from the compound system 44 Ti, produced via the α-cluster system 32 S + 12 C at 280 MeV, Planeta et al. [27] established that fragments (7  Z  16) were emitted due to symmetric splitting followed by evaporation. On the other hand, Oliveira et al. [28] have measured the energy-damped yield of binary fragments and quasi-elastic emission from the system 28 Si + 16 O, which produces the same composite 44 Ti at two different energies, viz. E c.m. = 39.10 and 50.5 MeV, respectively, and found that the Q-value-integrated angular distributions follows ∼1/sinθ c.m. -type behavior, indicating a long-lived intermediate state. However, the observation that the mass distributions peaks near to projectile and target mass, the ratio between the oxygen and carbon cross sections is rather large; and the total kinetic energy (TKE) values are significantly larger than the Coulomb repulsion, have conjectured the presence of the noncompound orbiting like mechanisms for the energy damped yield of the fragments from the system 28 Si + 16 O. Moreover, a large deformation has also been observed in the study of LCP emission from the same composite 44 Ti ∗ produced at different excitations via. the reaction 16 O (76, 96, 112 MeV) + 28 Si [29]. The observation of large deformation may be associated with orbiting process. Hence, a more detailed study of this system is necessary to delineate the fragment emission mechanism. Since Planeta et al. [27] made a detailed study for the fragments having atomic numbers (7  Z  16), it will, therefore, be worthwhile to study the emission of lighter fragments (Z  6) 2469-9985/2017/95(6)/064603(7) 064603-1 ©2017 American Physical Society