Role of the number of open channels in the dynamics of the dinucleus binary decay

Abstract

The occurrence of orbiting and fusion-fission processes observed experimentally in some light and medium-light heavy-ion collisions at incident energies well above the Coulomb barrier is discussed in the framework of a number of available open channels calculation. The fusion-fission mechanism appears to be less competitive in systems for which the available phase space for the highest partial waves is restricted to a few exit channels where dinuclear configurations can survive through orbiting trajectories. The coexistence of quasimolecular resonances, orbiting mechanisms, and the fusionfission process for medium-light dinuclei is also brie6y discussed.

Binary reaction decays fromMg24+C12

“…The underlying reaction mechanism is now fairly well established [27], and many of the barrier resonances appear to be correlated, indicating that a common structure is involved. This correlation strongly supports the hypothesis of the link between barrier resonances [2,4] in 12 C + 12 C and secondary minima in the compound nucleus (CN) 24 Mg [9,10,12]. Large quadrupole deformations (β 2 = 0.6-1.0) and α clustering in light N = Z nuclei are known to be general phenomena at low excitation energy.…”

“…The other gates correspond to energy regions where mutual inelastic excitation processes are dominant. The oscillations observed at large angles in the gate (a) region correspond to-as for the 24 Mg + 12 C exit-channel (not shown)-the oscillatory nature of the angular distribution of the α transfer, and they indicate the dominance of the grazing partial waves already observed for the 24 Mg + 12 C reaction [1,4,42,43] 16 O. The last two gates correspond to more and more energy damped collisions (deep-inelastic, orbiting [44] and fusion-fission [41]) with nonoscillatory angular distributions.…”

“…With the exception of the cluster decay of 60 Zn [32,33] and 56 Ni [34][35][36] recently studied using charged particle spectroscopy, no evidence for ternary breakup has yet been reported [13,[37][38][39][40][41] in light nuclei; the particle decay of 36 Ar SD bands (and other highly excited bands) is still unexplored. The main binary reaction channels of the 24 Mg + 12 C reaction, for which both quasimolecular structures [4,42,43] and orbiting phenomena [44] have been observed, is investigated in this work by using charged-particle-γ -ray coincidence techniques.…”

“…These resonances have been interpreted for 12 C + 12 C [2], the most favorable case for the observation of quasimolecular resonances [1][2][3][4][5], in terms of nuclear molecules. The question of whether the well-known 12 C + 12 C quasimolecular resonances represent true cluster states in the 24 Mg compound system or whether they simply reflect scattering states in the ion-ion potential is still unresolved [1,[6][7][8].…”

Dynamical decay of32S* and31P* formed in20Ne+12C and19F+12C reactions, respectively, atE*CN= 60 MeV

“…So instructively, both the compound systems are equally excited at the excitation energy E * CN =60 MeV, in order to compare their decays. is relevant to mention here that in the experimental study [2], both the 20 Ne+ 12 C and 19 F+ 12 C reactions have been investigated using the number of open channels (NOC) model [7] in which (Table I of [2]) they have pointed out that NOC for the later reaction are much more than in the former one. Hence, the measured C-yield, i.e., the Cyield Expt.…”