Multichannel Cluster Model Research Articles

Macroscopic versus microscopic models in predicting α-decay half-lives of actinide nuclei

This paper investigates the predictive power of the macroscopic and microscopic models in alpha-decay of actinide nuclei. Macroscopic theoretical models such as Coulomb and Proximity potential model (CPPM), Modified generalized liquid drop model (MGLDM) and Effective liquid drop model (ELDM) are applied in predicting the alpha-decay half-lives of actinide nuclei. The half-lives produced by these macroscopic models are compared with that of microscopic models such as Cluster model with two-potential approach (CM), Microscopic cluster model (MCM), Multichannel cluster model (MCCM) and that of experiments. The deviation of these models with the experiments is quantified using statistical treatment such as root mean square deviation [Formula: see text] (RMSD), mean deviation ([Formula: see text]), index [Formula: see text] and root mean square error (RMSE). It is found that among the microscopic and macroscopic models, ELDM and MCCM are, respectively, found to be accurate than that of other models. The microscopic model MCCM produces alpha-decay half-lives close to the experiments in the actinide region. The appropriate mass excess values have been identified to predict the exact alpha-decay half-lives in the actinide region.

Effects of nuclear collective vibrations on the α -decay fine structure of vibrational nuclei with A≈220

The multichannel cluster model (MCCM) is generalized to investigate the effect of nuclear collective vibrations on the $\ensuremath{\alpha}$-decay fine structure. Vibrational excitations up to two-phonon states are taken into account and coupled-channels calculations are performed for vibrational Rn, Ra, Th, and U isotopes. Without introducing any additional adjustable parameter, the calculated $\ensuremath{\alpha}$-decay branching ratios to various vibrational states show good agreement with the experimental data. In particular, it is shown that the $\ensuremath{\alpha}$-decay fine structure is strongly correlated with vibrational excitations, offering an alternative tool to explore the phonon states in daughter nuclei. Despite the $N=126$ shell closure, the calculated $\ensuremath{\alpha}$-decay half-lives are also found to be in good agreement with the experimental data. A unified description of the $\ensuremath{\alpha}$-decay fine structure has been achieved by the MCCM for both rotational and vibrational nuclei.

Systematics of fine structure in the α decay of deformed odd-mass nuclei

We present a detailed analysis of the a-decay fine structure in 32 deformed odd-mass nuclei from Z = 93 to Z = 102. The α-decay half-lives are systematically calculated within the multichannel cluster model (MCCM), which turns out to well reproduce the experimental data and show the neutron deformed shell structure. The branching ratios for various daughter states are investigated in the MCCM and in the WKB barrier penetration approach, respectively. It is found that the MCCM results agree well with the experimental data, while the WKB results have relatively large deviations from the experimental data for the α transitions to the high-lying members of the rotational band.

Coupled-channel representation to describe fine structure in theαdecay of odd-mass Bk isotopes

An extension of the multichannel cluster model (MCCM) is presented to investigate the a decay of odd-mass Bk isotopes from their ground states to more than one rotational band in the daughter Am nuclei. In these cases, the alpha intensity for the other rotational bands is comparable or dominant with respect to the favored one. Three rotational bands are taken into account for the alpha decays of Bk-243,Bk-245,Bk-247 from their 3/2(-) ground states. The available experimental data concerning fine structure and a-decay half-lives are well reproduced within the same framework. Moreover, the ground-state and favored rotational bands are considered for the alpha decay of Bk-249 from its 7/2(+) ground state. The calculated results also show good agreement with the latest experimental data [I. Ahmad et al., Phys. Rev. C 87, 054328 (2013)]. This is the first calculation of the alpha transitions to several rotational bands including favored and unfavored ones within the coupled-channel framework.

Theoretical description of fine structure in theαdecay of heavy odd-odd nuclei

The newly developed multichannel cluster model (MCCM), based on the coupled-channel Schrodinger equation with outgoing wave boundary conditions, is extended to study the alpha-decay fine structure in heavy odd-odd nuclei. Calculations are performed for the alpha transitions to favored rotational bands where the unpaired nucleons remain unchanged. The simple WKB barrier penetration formula is also used to evaluate the branching ratios for various daughter states. It is found that the WKB formula seems to overestimate the branching ratios for the second and third members of the favored rotational band, while the MCCM gives a precise description of them without any adjustable parameters. Moreover, the experimental total alpha-decay half-lives are well reproduced within the MCCM. DOI: 10.1103/PhysRevC.87.027602

Systematic Calculations of α-Decay Half-Lives of Well Deformed Nuclei

We perform an extensive investigation on the α decay of heavy deformed even-even and odd-A nuclei within the multichannel cluster model. The dynamics effects of core nuclei are taken into account in dealing with the interaction matrix and the α-cluster formation. Enough decay channels are considered for convergence in solving the coupled equations. Systematic calculations have been performed for 36 even-even nuclei and 32 odd-A nuclei. The calculated results show good agreement with the available experimental data concerning total α-decay half-lives and branching ratios, including the branching ratios for high-spin states.

Systematic calculation of fine structure in theαdecay of heavy odd-mass nuclei

The newly developed multichannel cluster model (MCCM) based on the coupled-channel Schrodinger equation with outgoing wave boundary conditions is extended to study the alpha-decay fine structure in heavy odd-A nuclei. More decay channels are considered for convergence in solving the coupled equations. Calculations are performed for 32 deformed nuclei with atomic numbers Z = 93-102. The branching ratios for various daughter states are well reproduced without any additional free parameters, and the calculated alpha-decay half-lives show good agreement with the experimental data. This indicates that the MCCM has universal applicability and equal validity regardless of even-even or odd-A alpha emitters.

Alpha-Decay Studies of Rf, Sg, and Hs Isotopes within the Multi-Channel Cluster Model

Besides alpha-decay energies and half-lives, more information on nuclear structure properties can be obtained from fine structure observed in a decay. The multi-channel cluster model (MCCM) for well-deformed alpha emitters has very recently been proposed for a precise description of the alpha-decay fine structure. In this paper, based on the neWly proposed Q alpha formula and the predicted rotational energy for superheavy nuclei, we present a theoretical prediction of the fine structure in the alpha decay of deformed Rf, Sg, and Hs isotopes within the MCCM. The branching ratios to various daughter states and total alpha-decay half-lives are evaluated by the five-channels microscopic calculations. Any adjustable parameter is not introduced in our calculations. This is, to our knowledge, the first coupled-channel study of the alpha-decay fine structure in superheavy nuclei. It is expected that the present predictions would be useful for ongoing or future experiments on structure researches of superhezwy nuclei.

Half-lives and fine structure for the α decay of deformed even-even nuclei

The alpha-decay properties of well-deformed even-even nuclei are systematically calculated within the multichannel cluster model (MCCM). Instead of working in the WKB framework, the quasibound solution to the coupled Schrodinger equation is presented with outgoing wave boundary conditions, and the coupling potential is taken into full account in terms of the general quantum theories. The calculated alpha-decay half-lives are found to agree well with the experimental data with a mean factor of less than 2. The fine structure observed in alpha decay is also well reproduced by the four-channel microscopic calculation. Very strikingly, the MCCM can give relatively precise descriptions of the branching ratio to excited 4(+) states, which is often overestimated in the usual WKB calculations. We expect it to be a significant development of theoretical models toward quantitative descriptions of alpha transitions to high-spin daughter states.

New approach forα-decay calculations of deformed nuclei

We present a new theoretical approach to evaluate $\ensuremath{\alpha}$-decay properties of deformed nuclei, namely the multichannel cluster model (MCCM). The deformed $\ensuremath{\alpha}$-nucleus potential is taken into full account, and the coupled-channel Schr\"odinger equation with outgoing wave boundary conditions is employed for quasibound states. Systematic calculations are carried out for well-deformed even-even nuclei with $Z\ensuremath{\geqslant}98$ and isospin dependence of nuclear potentials is included in the calculations. Fine structure observed in $\ensuremath{\alpha}$ decay is well described by the four-channel microscopic calculation, which is performed for the first time in $\ensuremath{\alpha}$-decay studies. The good agreement between experiment and theory is achieved for both total $\ensuremath{\alpha}$-decay half-lives and branching ratios to the ground-state rotational band of daughter nuclei. Predictions on the branching ratios to high-spin daughter states are presented for superheavy nuclei, which may be important to interpret future observations.

On the Anomalous Behaviour of the P-4He Elastic Scattering Polarization around 30 MeV

The experimentally observed structure in the p- 4 He elastic scattering polarization around 30 MeV is discussed in the framework of the multichannel cluster model. It is shown that its main features can be interpreted as an enhancement of the coupling between the 4 He-p and 3 He-d channels due to the presence of the 4 He * -p structure.

Lowest negative parity state ofBe8

Shell model and multichannel cluster model calculations yield different predictions for the lowest negative parity state of /sup 8/Be. Several shell model calculations predict a 1/sup -/ state below about 18.5 MeV which has the same quantum numbers as an ..cap alpha..-..cap alpha..* cluster state near 22 MeV. The experimental situation pertaining to this problem is examined.

Microscopic calculations for the 8Li system

A microscopic multi-channel cluster model calculation for the 8Li scattering system has been performed. Diagonal phase shifts, channel coupling strengths, and eigenphases are presented. For comparison, the 8Li bound and quasibound states have been investigated by a refined resonating group calculation. The results of both types of calculations are in excellent agreement. In the energy region up to the 5He-t threshold the calculated S-matrix elements, the energy eigenvalues, and the overlaps of the normalized functions with the eigenvectors explain the origin of the experimentally detected levels and moreover give predictions for the existence of additional levels.

A multichannel cluster model description for the 4He scattering system

A microscopic calculation for the 4He scattering system has been performed, which includes all possible two-body fragmentations: 3H-p, 3He-n and 2H- 2H. Simplified wave functions for the reacting particles lead to a very poor position for the 2H- 2H threshold. Sufficiently far from this threshold the calculated results are in good agreement with experimental data both for the elastic and inelastic processes. Possible modifications of the employed nucleon-nucleon model potential have been investigated.

Cluster model description of the d(α, αp)n break-up as two-step reaction

The 6Li scattering system has been described in the framework of the multichannel cluster model reaction theory. Under the assumption of sequential decay, cross sections for the 4He  d → 5He  p → 4He  n - p process have been calculated. Comparison of the theoretical results with recent experimental data shows good agreement for those kinematical situations, in which the sequential decay mechanism dominates.

An application of the multichannel cluster model theory to the elastic proton- α scattering

In the framework of the cluster model reaction theory a calculation for the elastic α-p scattering below 30 MeV was performed. The nucleon-nucleon potential, which contains spin orbit and tensor forces, has been succesfully used in reaction calculations for other light nuclei. The calculated α-p cross section and polarization values are in quantitative agreement with experimental data.