Orbiting in theC12+Ne

Abstract

The elastic scattering of heavy ions at large angles has received much attention since the measurements of Braun-Munzinger et at. 1 first revealed an enhanced cross section for scattering of 16 0+ 28 Si at center-of-mass angles larger than 100°. 2 The backward-angle enhancement seems to be a general feature for projectiles and targets in this mass region, although the size of the enhancement can vary markedly from system to system. A number of explanations have been offered for this phenomenon, such as Regge poles, 3 resonances, 4 parity-dependent potentials, 5 diffraction, 6 and particle exchange. 7 The regular broad structures appearing in the excitation functions could also be explained by orbiting in the mutual potential. 8 It would be desirable to have additional experimental data which might help in distinguishing among these various pictures. Since the interpretation of backward-angle enhancement in terms of the orbiting of projectile 6 M 0 Berlanger et al. 9 and target should have general consequences for inelastic scattering as well, 9 we have investigated the gross features of the inelastic scattering at backward angles. Experimental data of this type are reported here for the first time. We find both for the system 12 C + 20 Ne, on which we report here, and for other systems as well, 10 a strong enhancement of the cross section for inelastic scattering with large negative Q values at backward angles. The gross features we observe for the inelastic scattering find a natural interpretation in terms of orbiting and support this mechanism as the origin of backward-angle enhancement of elastic scattering as well.A natural carbon target was bombarded with beams of 50-to 80-MeV 20 Ne 4+ from the Oak Ridge isochronous cyclotron. The reaction products with Z> 3 were identified with a positionsensitive AE-E counter 11 which spanned an angular range of 9° in 1° steps. Angular distributions An experimental study of the 20 Ne + 12 C systems reveals a large cross section for inelastic scattering with large negative Q values at backward angles. The differential cross section is proportional to l/sin0 Coirio >100° and has characteristics consistent with the decay of an orbiting 20 Ne + 12 C dinuclear system.

Study of extreme nuclear shapes in extreme conditions

“…In the case of the α cluster 32 S nucleus, a highly deformed extended prolate configuration is evident which does not follow the usual evolution of shape with angular momentum. This unusual deformation, seen directly for the first time, can be speculated due to the formation of either the orbiting dinuclear configuration or molecular structure of 16 O+ 16 O in 32 S SD band.…”

“…However, it can also be conjectured that the observed unusual deformation can be due to the formation of the molecular structure of the 16 O+ 16 O cluster in 32 S. In the theoretical work of Kimura and Horiuchi [27], it was predicted that the SD states of 32 S have considerable amount of 16 O+ 16 O components and become more prominent as the excitation energy increases. The extracted deformation for two touching 16 O was found to be β = 0.73 which is in agreement with the experimentally extracted deformation from the resonance energy peaks. The occurrence of GDR in nuclei, where the entire nucleus takes part in a collective manner, is clearly an effect of the mean field structure of the nucleus.…”

“…For the α-like system, we have taken 20 Ne+ 12 C system and for a non-α-like system, we have chosen 20 Ne+ 27 Al system. The 20 Ne+ 12 C system is a well-established orbiting system [16], and our previous studies on enhancement of fragment yield near the entrance channel [17] as well as α-spectroscopic studies [18] have strongly indicated a highly deformed orbiting dinuclear shape for this system. On the contrary, for non-α-like 47 V system, it is well established that there is no significant entrance channel effect and fusion-fission compound nuclear yield is dominant in accordance with the qualitative expectation from the number of open channels model.…”

Characterization of fragment emission inNe20(7–10 MeV/nucleon)+C12Dey1, Bhattacharya2, Bhattacharya3 et al. 2007Phys. Rev. C19020View full textAdd to dashboardCite

“…Several experiments have been done in recent years to understand the mechanism of complex fragment emission in low-energy (E lab < ∼ 10 MeV/nucleon) light heavy-ion (A projectile + A target < ∼ 60) reactions [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. The origin of these fragments extends from quasi-elastic (QE)/ projectile breakup [2,3], deep-inelastic (DI) transfer and orbiting [4,6,12,13,14,15,16], to fusion-fission (FF) [18,19,20,21,22,23] processes; and in some cases the structure of the nuclei has been found to play an important role.…”

“…The inclusive energy distributions of the complex fragments (3 ≤ Z ≤ 7) emitted from the bombardment of 12 C by 20 Ne beams with incident energies between 145 and 200 MeV have been measured in the angular range 10 o ≤ θ lab ≤ 50 o . Damped fragment yields in all the cases have been found to have the characteristic of emission from fully energy equilibrated composites.…”