Evolution of fusion hindrance for asymmetric systems at deep sub-barrier energies

A Shrivastava,S Kailas,K Mahata,A Chatterjee,A Navin,K Ramachandran,C.S Palshetkar,S.K Pandit,P.C Rout,T Ichikawa,K Hagino,V.V Parkar,Abhinav Kumar,V Nanal

doi:10.1016/j.physletb.2016.02.029

Abstract

Measurements of fusion cross-sections of 7Li and 12C with 198Pt at deep sub-barrier energies are reported to unravel the role of the entrance channel in the occurrence of fusion hindrance. The onset of fusion hindrance has been clearly observed in 12C + 198Pt system but not in 7Li + 198Pt system, within the measured energy range. Emergence of the hindrance, moving from lighter (6,7Li) to heavier (12C,16O) projectiles is explained employing a model that considers a gradual transition from a sudden to adiabatic regime at low energies. The model calculation reveals a weak effect of the damping of coupling to collective motion for the present systems as compared to that obtained for systems with heavier projectiles.

Highlights

Fusion reactions in the vicinity of the Coulomb barrier have been investigated in the past to explore the mechanism of tunneling through multidimensional barriers, thereby giving an insight into the role of different intrinsic properties of the entrance channel
We discuss the general trend of fusion excitation function at deep sub-barrier energies for asymmetric systems involving light projectiles, namely, 6 Li + 198 Pt [22], 7 Li + 198 Pt, 12 C + 198 Pt and 16 O + 208 Pb [14,35]. 6,7 Li + 198 Pt are among the few systems, that have been probed for hindrance studies, having positive Q-values for the formation of compound nucleus [2]
The adiabatic model calculation indicates a weak effect of the damping for the present system as compared to that obtained for systems with heavier projectiles

Summary

Introduction

Fusion reactions in the vicinity of the Coulomb barrier have been investigated in the past to explore the mechanism of tunneling through multidimensional barriers, thereby giving an insight into the role of different intrinsic properties of the entrance channel. Recent efforts towards developing new methods to precisely measure very low fusion cross-sections have stimulated new activities, distinct to energies deep below the barrier Fusion data at these low energies can be uniquely used to interpret the reaction dynamics from the touching point to the region of complete overlap of the density distribution of the colliding nuclei, not accessible through any other reaction [1,2]. Deviation from a simple sudden picture is expected to occur for nuclei heavier than 4 He. The present work investigates the evolution of the fusion hindrance with increasing mass and charge of relatively light projectiles (6,7 Li, 12 C, 16 O) on heavy targets. The present work investigates the evolution of the fusion hindrance with increasing mass and charge of relatively light projectiles (6,7 Li, 12 C, 16 O) on heavy targets For this purpose we have performed new measurements at deep sub-barrier energies with. The current results along with the available data for different entrance channels have been studied to understand the origin of the fusion hindrance

Experimental details and results

Calculations

Findings

Discussion

Conclusion