Cluster radioactivity and clustering formation in nuclei

Physical Review C, 2003

The stability and/or instability of the deformed and superdeformed nuclei, 133−137 60 Nd, 144−158 64 Gd, [177][178][179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][192][193][194][195][196][197][198] Pb parents, coming from three regions of different superdeformations, are studied with respect to the α and heavy cluster decays. The α-decay studies also include the heavier 199−210 Pb nuclei, for reasons of spherical magic shells at Z=82 and N=126. The calculations are made by using the preformed cluster-decay model, and the obtained α-decay half-lives are compared with the available experimental data. Having met with a very good success for the comparisons of α-decay half-lives and in giving the associated known magic or sub-magic closed shell structures of both the parent nuclei and daughter products, the interplay of closed shell effects in the cluster-decay calculations is investigated. The clusterdecay calculations also give the closed shell effects of known spherical magicities, both for the parent and daughter nuclei, and further predict new (deformed) closed shells at Z=72-74 and N=96-104 due to both the stability and instability of Hg and Pb parents against cluster decays. Specifically, a new deformed daughter radioactivity is predicted for various cluster decays of [186][187][188][189][190]195 Pb parents with the best possible measurable cases identified as the 8 Be and 12 C decays of 176,177 Hg and/or 192 Pb parents. The predicted decay half-lives are within the measurable limits of the present experimental methods. The interesting point to note is that the parents with measurable cluster decay rates are normal deformed nuclei at the transition between normal and superdeformation.

Nuclear Physics A, 2004

A cluster model is applied to the description of the ground state alternating parity bands in actinides and some Ba and Ce isotopes and to the description of the superdeformed band in 'jOZn. The model is based on the assumption that cluster-type shapes are produced by a collective motion of the nuclear system in the mass asymmetry coordinate.

2019

The clustering effects in light mass alpha conjugate 20 Ne, 28 Si and non-alpha conjugate 21 Ne, 22 Ne nuclear systems have been investigated comparatively, within the collective clusterization approach of dynamical cluster-decay model. The evolution of cluster structure with temperature at three different temperatures corresponding to ground state, Ikeda's threshold energy and experimentally available energy has been made by taking into account the modified pairing strength in liquid drop energies. The results present that in addition to xα-type clusters (x is an integer) and xn-xα type clusters in alpha conjugate and non-alpha conjugate nuclear systems, respectively, np-xα type (n-neutron, p-proton) clusters are also preformed significantly at higher experimental excitation energy due to decreased pairing strength in liquid drop energies with rising temperature. Further, the fragmentation analysis has been undertaken at higher excitation energies to explore the reaction mechanism in the decay of different Z = 5, 6, 7 (or complementary Z = 3, 4, 5) fragments/clusters in reference to experimentally available Z-distribution data. The analysis depicts the presence of competing mechanisms of fusion-fission (FF) and deep inelastic orbiting (DIO) in the decay path, where the contribution of DIO cross-section σ DIO has been evaluated empirically. The higher contribution of σ DIO has been found for C-yield in all three 20 Ne * , 21 Ne * and 22 Ne * nuclear systems and the experimental verification is called for the same. The DCM calculated total cross-sections for different Z-fragments are in agreement with the experimental data.

A clusterization theory is presented to describe the clusterization probability (preformation factor). The clusterization states are described as a quantum-mechanical cluster-formation state in a proposed cluster-formation model to determine the preformation factor of alpha-decay process in radioactive nuclei. The formation of alpha particle inside the parent nuclei is considered within two postulates; the compound nucleus of Bohr's assumption and the surface effect. The total and formation energy are obtained from the from the binding energies differences. This model is tested for 212 Po for the alpha-cluster decay. The calculated preformation factor 0.54 has shown good agreements with that of some others as reported. As such, this model could give more insight to the understanding of the nuclear structure in the radioactive nuclei.

International Journal of Modern Physics E, 2006

The entrance-channel effects in the decay of hot and rotating compound nucleus 48 Cr * , formed in symmetric 24 Mg + 24 Mg and asymmetric 36 Ar+ 12 C reactions, are studied as collective clusterization process, for emissions of both the light particles (LPs) as well as the intermediate mass fragments (IMFs), with in the dynamical cluster-decay model (DCM). We find that the little differences observed in the decay of equilibrated compound nucleus 48 Cr * , formed in the two entrance channels with about the same excitation energy, are not in variance with the Bohr's independence hypothesis. In other words, the present study confirms the entrance-channel independence of the decay of compound nucleus 48 Cr * formed due to different target-projectile combinations with similar excitation energies. The collective clusterization process is shown to contain the complete structure of the measured fragment cross sections as well as average total kinetic energies.

arXiv (Cornell University), 2024

A detailed study of α-clusters decay is exhibited by incorporating crucial microscopic nuclear structure information into the estimations of half-life and preformation factor. For the first time, using the k-cross validation approach, two semi-empirical formulas for (i) α-decay half-life and (ii) α-particle preformation factor, are picked out and subsequently modified by including shell, odd-nucleon blocking, and asymmetry effects along with the usual dependence on α-decay energy (Q α) and angular momentum of α-particle. Both the formulas are fitted for the two different regions separated by neutron number N=126, as from the experimental systematics the role of N=126 shell closure is found decisive in determining the trends of Q α , α-decay half-life, and α-particle preformation factor. It is found that the inclusion of the above-mentioned degrees of freedom significantly reduces the errors in the estimations when compared with several other similar modified/refitted semi-empirical relations indicating the robustness of the proposed formulas. The predictions of α-decay half-life throughout the periodic chart have been made including the unknown territory, future probable decay chain of self-conjugate nucleus 112 Ba terminated on 100 Sn, decay chain of 208 Pa through new isotope 204 Ac as well as decay chains of awaiting superheavy nuclei 298 Og and 299 120. This article is expected to provide a systematic approach to selecting the formula by which reliable predictions can be made.

International Journal of Modern Physics E-nuclear Physics, 2006

The entrance-channel effects in the decay of hot and rotating compound nucleus 48Cr*, formed in symmetric 24Mg+24Mg and asymmetric 36Ar+12C reactions, are studied as collective clusterization process, for emissions of both the light particles (LPs) as well as the intermediate mass fragments (IMFs), with in the dynamical cluster-decay model (DCM). We find that the little differences observed in the decay of equilibrated compound nucleus 48Cr*, formed in the two entrance channels with about the same excitation energy, are not in variance with the Bohr's independence hypothesis. In other words, the present study confirms the entrance-channel independence of the decay of compound nucleus 48Cr* formed due to different target-projectile combinations with similar excitation energies. The collective clusterization process is shown to contain the complete structure of the measured fragment cross sections as well as average total kinetic energies.

EPJ Web of Conferences, 2016

Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly simple for investigations of α-particle clustering (because α-particle has J π =0 + , which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10 B+ 10 B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay. Clustering was recognized [1] as an essential ingredient in description of light nuclei already in the early days of nuclear physics, even before the actual formulation of nuclear shell model. A systematic picture of the phenomenon for the α-conjugate nuclei (with N =Z) emerged in the late sixties, 201 , 0 0 EPJ Web of Conferences

Journal of Nuclear Physics, Material Sciences, Radiation and Applications

Based on the Coulomb and Proximity Potential Model, we have studied the decay probabilities of various exotic nuclei from even-even nuclei in the super heavy region. The half-lives and barrier penetrability for the decay of exotic nuclei such as 7-9B, 16-19 Ne, 8-11 C, 23-30 P and 26-32 S from the isotopes 274-332116,274-334 118 and 288-334120 are determined by considering them as spherical as well as deformed nuclei. The effect of ground state quadrupole (β2), Octupole (β3) and hexadecapole (β4) deformation of parent, daughter and cluster nuclei on half- lives and barrier penetrability were studied. Calculations have done for the spherical nuclei and deformed nuclei in order to present the effects of the deformations on half-lives. It is found that height and shape of the barrier reduces by the inclusion of deformation and hence half-life for the emission of different clusters decreases and barrierpenetrability increases. Changes in the half-lives with and without the inclusion of ...

Physical Review C, 2010

The relativistic mean-field (RMF) theory is used to obtain the nuclear matter densities for the double folding procedure used to construct the cluster-daughter potential with M3Y nucleon-nucleon interaction including exchange effects. Following the PCM approach, we have deduced empirically the preformation probability P 0 emp from the experimental data on both the αand exotic cluster-decays, specifically of parents in the trans-lead region having doubly magic 208 Pb or its neighboring nuclei as daughters. Interestingly, the RMF-densities-based nuclear potential supports the concept of preformation for both the α and heavier clusters in radioactive nuclei. P 0 α(emp) for α decays is almost constant (∼10 −2-10 −3) for all the parent nuclei considered here, and P 0 c(emp) for cluster decays of the same parents decrease with the size of clusters emitted from different parents. The results obtained for P 0 c(emp) are reasonable and are within two to three orders of magnitude of the well-accepted phenomenological model of Blendowske-Walliser for light clusters.

Physical Review C, 2022

Background: The cluster radioactivity from the neutron-deficient trans-tin region of the nuclear landscape has given immediate attention in the nuclear structure studies. Recent prediction of the emitting clusters from the ground and intrinsic excited states of proton-rich Ba isotopes opens the direction to explore the corresponding decay characteristics. A theoretical probe is necessary for understanding the cluster decays of Ba isotopes. Purpose: In the present study, cluster-decay half-lives are calculated and their decay characteristics are investigated for even-even 112-122 Ba isotopes in both ground and intrinsic excited states along the proton drip line. Method: The preformed-cluster-decay model (PCM) is employed for estimating the decay half-lives. The preformation probability (P 0) of the cluster decay from the parent nuclei is calculated by using the well-known phenomenological formula of Blendowske and Walliser [Phys. Rev. Lett. 61, 1930 (1988)], supplemented with the newly proposed Q-value-based preformation factor for the cluster with mass A c > 28. The penetration probability is calculated from the interaction potential using the Wentzel-Kramers-Brillouin (WKB) approximation. The nucleon-nucleon (NN) potential and individual binding energy (BE) of the cluster and daughter nuclei are estimated from the microscopic relativistic mean-field formalism (RMF) and compared with those from experiments and the finite-range-droplet model for the estimation of the Q values of the cluster decays. The nonlinear RMF Lagrangian from which the effective relativistic R3Y NN potential is derived using the NL3 * parameter set is employed for the calculation of the nuclear matter densities. The R3Y and well-known M3Y potential are employed to obtain the cluster-daughter interaction potential using the double-folding procedure along with their corresponding RMF densities. The total potential along with their respective cluster decay Q values are used as input in the PCM to obtain the half-lives (T 1/2) of 112-122 Ba isotopes in their ground and intrinsic excited states. Results: The calculated half-lives (T 1/2) for relativistic R3Y NN potential and Q values are found to deviate slightly compared to the ones from the M3Y due to the difference in their barrier characteristics. We notice that at elongated neck configuration a minimum neck-length parameter R = 1.0 fm is required for R3Y potential due to its repulsive nature, whereas the value is 0.5 fm is suitable for the M3Y case. However, the estimated decay half-lives for both the potentials are in reasonably good agreement with the experimental lower limit of 114 Ba. In contrast with the ground-state decays, the inclusion of intrinsic excitation reduces the corresponding half-life values considerably but does not rule out the role of magicity. Conclusions: The sensitivity of the decay half-lives to Q values and neck-length parameter has also been demonstrated. The decay half-lives are predicted for various cluster decays from neutron-deficient Ba isotopes. Since none of the experimental half-lives for the examined clusters is precisely known yet, further studies with available observed half-lives will be needed to substantiate our findings.

Nuclear physics a, 2022

The alpha decay, the cluster radioactivity and the heavy particle emission half-lives of known and some still unknown superheavy nuclei have been investigated within the original Generalized Liquid Drop Model and analytic formulas. The Q value has been calculated mainly from the recent NUBASE2020 tables. The agreement between the experimental data and the theoretical predictions of the alpha decay half-lives of the superheavy nuclei is correct and some predictions are provided for unknown nuclei. For some emissions of heavy particles by superheavy nuclei the half-life is comparable to the alpha decay half-lives or even smaller.

Physical Review D, 1984

Brief Reports Brief Reports are short papers which report on completed research which, while meeting the usual Physical Review standards of scientific quality, does not warrant a regular article. (Addenda to papers previously published in the Physical Review by the same authors are included in Brief Reports.) A Brief Report may be no longer than 3% printed pages and must be accompanied by an abstract. The same publication schedule as for regular articles is followed, and page proofs are sent to authors.

2011

A great deal of research work has been undertaken in the α-clustering study since the pioneering discovery, half a century ago, of 12 C + 12 C molecular resonances. Our knowledge in the physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. In this work, the occurence of "exotic" shapes in light N = Z α-like nuclei is investigated. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Results on clustering aspects are also discussed for light neutron-rich oxygen isotopes.

AIP Conference Proceedings, 2004

It is shown that the static and dynamic cc-cluster models of nuclei, which describe an elastic electron scattering, photodisintegration reactions and pion double charge exchange reactions on a-cluster nuclei are in favor of the a-capture and a process of the formation of these nuclei.