Coupled-Channel Effects in Collisions Between Heavy Ions Near the Coulomb Barrier
With the recent availability of state-of-the-art heavy-ion stable and radioactive beams, there has been a renew interest in the investigation of nuclear reactions with heavy ions. I first present the role of inelastic and transfer channel couplings in fus
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Abstract With the recent availability of state-of-the-art heavy-ion stable and radioactive beams, there has been a renew interest in the investigation of nuclear reactions with heavy ions. I first present the role of inelastic and transfer channel couplings in fusion reactions induced by stable heavy ions. Analysis of experimental fusion cross sections by using standard coupled-channel calculations is discussed. The role of multi-neutron transfer is investigated in the fusion process below the Coulomb barrier by analyzing 32 S + 90,96 Zr as benchmark reactions. The enhancement of fusion cross sections for 32 S+ 96 Zr is well reproduced at sub-barrier energies by NTFus code calculations including the coupling of the neutron-transfer channels following the Zagrebaev semi-classical model. Similar effects for 40 Ca + 90 Zr and 40 Ca + 96 Zr fusion excitation functions are found. The breakup coupling in both the elastic scattering and in the fusion process induced by weakly bound stable projectiles is also shown to be crucial. In this lecture, full coupled-channel calculations of the fusion excitation functions are performed by using the breakup coupling for the more neutron-rich reaction and for the more weakly bound projectiles. I clearly demonstrate that Continuum-Discretized Coupled-Channel calculations are capable to reproduce the fusion enhancement from the breakup coupling in 6 Li + 59 Co.
1 Introduction Heavy-ion fusion reactions at bombarding energies at the vicinity and below the Coulomb barrier have been widely studied [1–5]. In low-energy fusion reactions, the very simple one-dimensional barrier-penetration model (1D-BPM) [1, 2] is based upon a real potential barrier resulting from the attractive nuclear and repulsive C. Beck (B) Institut pluridisciplinaire Hubert Curien, IN2P3-CNRS and Université de Strabourg—23, rue du Loess BP 28, 67037 Strasbourg Cedex 2, France e-mail: [email protected] W. Greiner (ed.), Exciting Interdisciplinary Physics, FIAS Interdisciplinary Science Series, DOI: 10.1007/978-3-319-00047-3_9, © Springer International Publishing Switzerland 2013
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Coulomb interactions. For light- and medium-mass nuclei, one only assumes that the di-nuclear system (DNS) fuses as soon as it has reached the region inside the barrier i.e. within the potential pocket. If the system can evolve with a bombarding energy high enough to pass through the barrier and to reach this pocket with a reasonable amount of energy, the fusion process will occur after a complete amalgamation of the colliding nuclei forming the compound nucleus (CN). On the other hand, for sub-barrier energies the DNS has not enough energy to pass through the barrier. In reactions induced by stable beams, the specific role of multi-step nucleontransfers in sub-barrier fusion enhancement still needs to be investigated in detail both experimentally and theoretically [6–14]. In a complete description of the fusion dynamics the transfer channels in standard coupled-channel (CC) calculations [2, 8, 10, 14, 15] have t
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