Caloric curve in Au + Au collisions

Realistic caloric curves are obtained for $^{197}Au + ^{197}Au$ reaction with incident energy ranging from 35 to 130 MeV/nucleon in the dynamic statistical multifragmentation model. It is shown that for excitation energy 3 to 8 MeV/nucleon, the temperature remains constant in the range 5 to 6 MeV, which is close to experiment. The mechanism of energy deposition through the tripartition of colliding system envisaged in this model together with inter-fragment nuclear interaction are found to play important role. A possible signature of liquid-gas phase transition is seen in the specific heat distribution calculated from these caloric curves, and the critical temperature is found to be $\sim$ 6 to 6.5 MeV.Comment: Revtex, 10 pages, 4 postscipt figures, To appear in Phys. Rev. C (Rapid Communications

Effect of projectile on incomplete fusion reactions at low energies

Present work deals with the experimental studies of incomplete fusion reaction dynamics at energies as low as ≈ 4 - 7 MeV/A. Excitation functions populated via complete fusion and/or incomplete fusion processes in 12C+175Lu, and 13C+169Tm systems have been measured within the framework of PACE4 code. Data of excitation function measurements on comparison with different projectile-target combinations suggest the existence of ICF even at slightly above barrier energies where complete fusion (CF) is supposed to be the sole contributor, and further demonstrates strong projectile structure dependence of ICF. The incomplete fusion strength functions for 12C+175Lu, and 13C+169Tm systems are analyzed as a function of various physical parameters at a constant vrel ≈ 0.053c. It has been found that one neutron (1n) excess projectile 13C (as compared to 12C) results in less incomplete fusion contribution due to its relatively large negative α-Q-value, hence, α Q-value seems to be a reliable parameter to understand the ICF dynamics at low energies. In order to explore the reaction modes on the basis of their entry state spin population, the spin distribution of residues populated via CF and/or ICF in 16O+159Tb system has been done using particle-γ coincidence technique. CF-α and ICF-α channels have been identified from backward (B) and forward (F) α-gated γspectra, respectively. Reaction dependent decay patterns have been observed in different α emitting channels. The CF channels are found to be fed over a broad spin range, however, ICF-α channels was observed only for high-spin states. Further, the existence of incomplete fusion at low bombarding energies indicates the possibility to populate high spin state

Effect of the Target Deformation on Incomplete Fusion Dynamics

Abstract. To investigate the role of target deformation on incomplete fusion dynamics, a particle-gamma coincidence experiment has been performed at Inter University Accelerator Centre, New Delhi. Spin distributions for various evaporation residues populated via complete and incomplete fusion of 16O with 124Sn at 6.3MeV/nucleon have been measured. Experimentally measured spin distributions of the residues produced as incomplete fusion products associated with fast α and 2α-emission channels observed in forward cone are found to be distinctly different from those of the residues produced as complete fusion products. The mean value of input angular momentum J0 for evaporation residues produced through xn channels (complete fusion products) is found to be J0 ≈ 7ħ, while the mean value of input angular momentum J0 for the residues produced through direct αxn and 2αxn channels (incomplete fusion products) in forward cone, are found to be J0 ≈ 9ħ and ≈ 12ħ respectively for 16O + 124Sn (spherical) system [7]. The mean value of input angular momentum J0 for the system 16O + 169Tm (deformed) reported in ref. [8], are found to be ≈10ħ for xn-channels (complete fusion products) and for direct αxn and 2αxn channels (incomplete fusion products) the value of J0 approaches to ≈ 13ħ and ≈16ħ, respectively. The mean values of the input angular momentum observed for xn (complete fusion products), αxn and 2αxn (incomplete fusion products) in 16O + 124Sn (spherical) system are smaller than that of the mean values of the input angular momentum observed for xn (complete fusion products), αxn an

Investigation of the influence of incomplete fusion on complete fusion of 16O induced reactions at moderate excitation energies

An attempt has been made to investigate for the reaction dynamics leading to incomplete fusion (ICF) of heavy ions at moderate excitation energies, especially the influence of incomplete fusion on complete fusion (CF) of 16O induced reactions at specific energies. Excitation functions (EFs) of various reaction products populated via CF and/or ICF of 16O projectile with 45Sc target were measured at energies ≈3-7 MeV/nucleon, using recoil catcher technique followed by offline γ-ray spectroscopy. The measured EFs were compared with theoretical values obtained using the statistical model code PACE4. The experimentally measured EFs were in general found to be in good agreement with the theoretical predictions for non α-emitting channels in the present target projectile system. However, for α-emitting channels the measured EFs were higher than the predictions of the theoretical model codes, which may be credited to incomplete fusion reactions at these energies

Observation of incomplete fusion at low angular momenta

Present work deals with experimental studies of incomplete fusion reaction dynamics using off-line γ-ray spectrometry at energies as low as ≈3-6 MeV/nucleon. Excitation functions for five reaction products populated via complete and/or incomplete fusion processes in 16O+130Te system have been measured and compared with the predictions of the statistical model code PACE4. A significant enhancement in the measured excitation functions compared to theoretical predictions for α-emitting channels has been observed and is attributed to incomplete fusion processes. The relative strength of incomplete fusion has been found to increase with projectile energy. Results show that incomplete fusion is associated even for angular momenta lesser than the critical angular momentum for complete fusion and also reveals importance of incomplete fusion even at energies as low as ≈3-6 MeV/nucleon

Incomplete fusion reactions at low energies in 13

Aiming to investigate the incomplete fusion processes at low projectile energies, experiments have been carried out for the 13C + 169Tm system at ≈ 4-7 MeV/A. Excitation functions for several heavy residues likely to be populated via complete and incomplete fusion processes have been measured using heavy recoil residue catcher technique followed by γ- ray spectroscopy. The measured cross-sections for the complete fusion (xn and pxn) channels are compared with the statistical model code PACE4, consistently using the same set of parameters. The complete fusion channels are found to be consistent with the model calculations. However, the cross-sections for all the measured α-emitting channels are found to be significantly enhanced over the calculations. Analysis of data indicate a significant fraction of incomplete fusion even at energies as low as 17% above barrier. The present results are discussed in light of the Morgenstern’s systematics. Incomplete fusion strength function is found to be relatively large for alpha cluster projectile i.e. for 12C as compared to one neutron excess 13C projectile