Fusion in 6 Li + 197 Au at near barrier energies Shital Thakur 1* , Vivek Singh 1 , C.S. Palshetkar 2 , V. Nanal 1 , R.G. Pillay 1 , A. Shrivastava 2 , P.C. Rout 2 , K. Ramachandran 2 and A. Chatterjee 2 1 Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai - 400005, INDIA 2 Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, INDIA *email: shital_t@yahoo.co.in Introduction: The study of effect of breakup on fusion processes with weakly bound nuclei at near barrier energies has gained importance in recent years [1]. In order to gain insight into the influence of the projectile structure on the fusion process, we have carried out measurements with 6,7 Li on 197 Au. Amongst stable nuclei, 6 Li has the lowest breakup threshold S α/d =1.475MeV. In this paper we present fusion excitation function of 6 Li + 197 Au over the energy range 0.8 ≤ E/V b ≤ 1.5. The fusion excitation function for 7 Li (S α/t =2.45MeV) + 197 Au over a range 0.6 ≤ E/V b ≤ 1.5 was reported earlier [2]. Experimental Details: The experiment was performed at Pelletron LINAC facility, Mumbai with 6 Li beam of 10-20 pnA. The targets of 197 Au foils of thickness 1.25-2 mg/cm 2 were irradiated at beam energies from 26MeV to 44MeV in steps of 2MeV. The experimental setup and offline data collection procedures are similar to the earlier measurement [2]. For efficient use of beam time, two cascaded targets with Al foil of appropriate thickness as a degrader (~1-3 MeV loss) were used in this experiment. The energy after the degrader was calculated using TRIM [3]. At lowest energies the data was collected in a close geometry inside the lead house. Table 1 lists the characteristic γ-rays and half-lives of different reaction products. All the fusion and transfer products could be clearly identified and half-lives also have been verified. Table 1: Characteristic γ-rays and half-lives Nuclide E γ (keV) T 1/2 201 Pb (2n) 331.15 9.33 hrs 200 Pb (3n) 257.19, 268.36 21.5 hrs 199 Pb (4n) 353.39,720.24 90 min 198 Pb (5n) 173, 290 2.4hrs 198 Au (1n-stripping) 411.8 2.69 days 196 Au (1n-pickup) 333.03, 355.7 6.17 days 197m Hg (d,2n) 134 23.8hrs Figure 1: Measured excitation function (symbols) for residues from complete fusion in 6 Li+ 197 Au reaction together with statistical model PACE calculations (lines). The excitation functions of the direct reaction channels namely, 1n-pickup and 1n stripping are shown in figure 2. In case of a d/t transfer, the products (Hg isotopes) are stable and could not be measured by present technique However, 197m Hg (13/2 + ) arising from (d,2n) is observed. Proceedings of the DAE Symp.on Nucl. Phys. 55 (2010) 294 Avilable online at www.sympnp.org/proceedings