Publisher’s Note: Cluster decay of hot56Ni⋆formed in the32

Abstract

The decay of56 N i * , formed in 32 S + 24 M g reaction at the incident energies Ecm=51.6 and 60.5 MeV, is calculated as a cluster decay process within the Preformed Cluster-decay Model (PCM) of Gupta et al. re-formulated for hot compound systems. Interesting enough, the cluster decay process is shown to contain the complete structure of both the measured fragment cross sections and total kinetic energies (TKEs). The observed deformed shapes of the exit channel fragments are simulated by introducing the neck-length parameter at the scission configuration, which nearly coincides the 56 N i saddle configuration. This is the only parameter of the model, which though is also defined in terms of the binding energy of the hot compound system and the ground-state binding energies of the various emitted fragments. For the temperature effects included in shell corrections only, the normalized α-nucleus s-wave cross sections calculated for nuclear shapes with outgoing fragments separated within nuclear proximity limit (here ∼0.3 fm) can be compared with the experimental data, and the TKEs are found to be in reasonably good agreement with experiments for the angular momentum effects added in the sticking limit for the moment of inertia. The incident energy effects are also shown in predicting different separation distances and angular momentum values for the best fit. Also, some light particle production (other than the evaporation residue, not treated here) is predicted at these energies and, interestingly, 4 He, which belongs to evaporation residue, is found missing as a dynamical cluster-decay fragment. Similar results are obtained for temperature effects included in all the terms of the potential energy. The non-α fragments are now equally important and hence present a more realistic situation with respect to experiments. [2][3][4][5][6][7][8]). At such incident energies, the incident flux is found to get trapped by the formation of a compound nucleus (CN), which is in addition to a significant large-angle elastic scattering cross section. For lighter masses (A CN < 44), such a compound nucleus decays subsequently by the emission of mainly light particles (n, p, α) and γ-rays; i.e. with very small component of heavy fragment (A > 4) emission. An experimental measure of this so-called particle evaporation residue yield is the CN fusion cross section. For somewhat heavier systems, like 48 Cr and 56 N i, a significant decay strength to A > 4 fragments, the mass-asymmetric channels, is also observed which could apparently not arise from a direct reaction mechanism because of the large mass-asymmetry differences between the entrance and exit channels. The measured angular distributions and energy spectra are consistent with fission-like decays of the respective compound systems. PACSFor the 32 S + 24 M g → 56 N i * reaction, in one of the experiments, the mass spectra for A=12 to 28 fragments and the total kinetic energy (TKE) for only the most favoured (enhanced yields) α-nucleus fragments are measured at the energies E ...

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

“…Moreover, in general, all the IMFs in the decay of 32 S * and 31 P * are favoured at the higher -values, which is true for the LPs at the lower -values or vice-versa. The trend for the LPs as well as IMFs observed here is in line with that for the light mass compound nuclei [3,4]. Fig.…”

“…The DCM [3][4][5], based on the quantum mechanical fragmentation theory (QMFT), is worked out in terms of the collective coordinates of mass asymmetry η = A 1 −A 2 A 1 +A 2 and relative separation R, which allows to define the decay cross-section, as…”

“…The decay of very light mass compound nuclei 32 S * and 31 P * formed in 20 Ne+ 12 C and 19 F+ 12 C reactions, respectively, are studied here using the Dynamical Clusterdecay Model (DCM) of Gupta and collaborators [3][4][5]. In a e-mail: birbikram.singh@gmail.com terms of the barrier picture, a cluster-decay process in this model is in fact a fission process with structure effects of the CN also included via the preformation probabilities P 0 of the fragments.…”

“…The processes of fusion-fission (ff) and a deep inelastic (DI) orbiting mechanism are in competition for these systems [1,2]. In the ff mechanism, a completely equilibrated compound nucleus (CN) is formed, which decays into various exit channels, independent of entrance channel but depending on their masses [3][4][5], whereas in a deep inelastic (DI) orbiting mechanism a long lived dinuclear molecular system is formed with strong memory of entrance channel which subsequently decays into targetprojectile like fragments and contribute σ orb to the overall decay cross section. For a very light compound system, standard rotating liquid drop model (RLDM) predicts strong inhibition of ff mechanism, as compared to DI scattering/ orbiting process [6].…”

Role of rotational energy component in the dynamics of 16O+198Pt reaction

“…So, it is of further interest to study the effect of long range interaction potential (centrifugal part) in the decay processes (evaporation residue and a e-mail: msharma@thapar.edu fission) of CN. In the present work, centrifugal potential is investigated within two limits of momentum of inertia such as (i) Sticking limit I S [9] (ii) Non Sticking limit I NS [6]. There are various hypothesis other than these two limits such as rolling and sliding conditions.…”