Fusion ofCa48+Zr90,96above and below the Coulomb barrier

Abstract

Fusion-evaporation cross sections were measured in the two systems 48 Ca + 90,96 Zr in an energy range from well below to well above the Coulomb barrier. The sub-barrier fusion of 48 Ca + 90 Zr is reproduced by coupled-channels calculations including the lowest quadrupole and octupole vibrations of 90 Zr, and using a Woods-Saxon potential with a standard diffuseness parameter a = 0.68 fm. However, the fusion cross sections are overestimated above the barrier. The low-energy slope of the excitation function for 48 Ca + 96 Zr is steeper. This implies a larger diffuseness parameter a = 0.85 fm. Fusion cross sections are well fit in the whole energy range, and the effect of the strong octupole vibration in 96 Zr is predominant. The extracted fusion barrier distributions are reasonably well reproduced by calculations for both systems. A comparison with previous data for 40 Ca + 90,96 Zr is made in an attempt to clarify the role of transfer couplings in sub-barrier fusion.

Examining the role of transfer coupling in sub-barrier fusion ofTi46,50+Sn124

“…5 [12,13], and (f) 58,64 Ni+ 132 Sn [10,11] are compared where the reaction energy is shown on a reduced scale using the barrier height predicted by the frozen HF. the larger sub-barrier fusion enhancement has in the past been attributed to the coupling to neutron transfer [5,7,8,26]. However, if the the same reasoning is applied to 58 Ni and 64 Ni induced fusion on 124 Sn and 132 Sn then the sub-barrier fusion enhancement is expected to be larger for 58 Ni induced reactions.…”

Coupled-Channel Effects in Collisions Between Heavy Ions Near the Coulomb Barrier

“…The small enhancement as compared to the reference (tightly bound) system 16 O+ 58 Ni is here related to the low binding energy of the 17 F valence proton. This moderate effect is mainly triggered from a transfer effect, as observed for the 2n-halo 6 He [18,19] and the 1n-halo 11 Be [42] in contrast to the 1p-halo 8 B+ 58 Ni reaction where strong enhancements are trigerred from a breakup process [45].…”

“…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 [6,7,8,9,10,11,12,13,14]. In a complete description of the fusion dynamics the transfer channels in standard coupled-channel (CC) calculations [2,8,10,14,15] have to be taken into account accurately.…”

Nuclear reactions studied by quasi-elastic measurements with high precision at backward angles

“…However, large numbers of open questions still remain to be solved, for instance, i) the surface diffuseness anomaly in interaction potential [1][2][3], ii) the coupled-channels effects of neutron transfers with positive Q value [4][5][6], iii) the breakup effects of weakly-bound nuclei on the fusion processes [7][8][9][10], and so on. Quasi-elastic scatterings and fusion reactions are complementary processes because they undergo the same interaction potential and share the mutual information on the reaction mechanism.…”