A. T. Kruppa

A program for coupled-channel calculations with all order couplings for heavy-ion fusion reactions

A FORTRAN 77 program that calculates fusion cross sections and mean angular momenta of the compound nucleus under the influence of couplings between the relative motion and several nuclear collective motions is presented. The no-Coriolis approximation is employed to reduce the dimension of coupled-channel equations. The program takes into account the effects of nonlinear couplings to all orders, which have been shown to play an important role in heavy-ion fusion reactions at subbarrier energies.

Shell corrections of superheavy nuclei in self-consistent calculations

Shell corrections to the nuclear binding energy as a measure of shell effects in superheavy nuclei are studied within the self-consistent Skyrme-Hartree-Fock and relativistic mean-field theories. As a result of the presence of a low-lying proton continuum resulting in a free particle gas, special attention is paid to the treatment of the single-particle level density. To cure the pathological behavior of the shell correction around the particle threshold, a method based on the Greens function approach has been adopted. It is demonstrated that for the vast majority of Skyrme interactions commonly employed in nuclear structure calculations, the strongest shell stabilization appears for Z=124 and 126, and for N=184. On the other hand, in the relativistic approaches the strongest spherical shell effect appears systematically for Z=120 and N=172. This difference probably has its roots in the spin-orbit potential. We have also shown that, in contrast to shell corrections which are fairly independent of the force, macroscopic energies extracted from self-consistent calculations strongly depend on the actual force parametrization used. That is, the A and Z dependence of the mass surface when extrapolating to unknown superheavy nuclei is prone to significant theoretical uncertainties. (c) 2000 The American Physical Society.

Fine Structure in the Decay of Deformed Proton Emitters: Nonadiabatic Approach

The coupled-channel Schrodinger equation with outgoing wave boundary conditions is employed to study the fine structure seen in the proton decay of deformed even- N, odd- Z rare earth nuclei 131Eu and 141Ho. Experimental lifetimes and proton-decay branching ratios are reproduced. Variations with the standard adiabatic theory are discussed.

α-particle decay through a deformed barrier

Abstract The eigenchannel formalism of sub-barrier fusion is extended to the α-decay of even-even nuclei. Despite an enormous advantage attainable by transmission through the maximum-flux eigenchannel, corresponding to penetration through the low barrier polar region of the deformed prolate daughter, branching ratios suggest that deformed actinide nuclei take a different decay path imposed by the preformed angular momentum superposition in the nuclear interior. Using both WKB and coupled-channels transmission matrices, we have found that all known branching ratios of even-even actinide nuclei can be fitted with essentially the same internal amplitudes. Under the assumption that daughter states do not mix during barrier penetration, these same amplitudes also give good results for the known anisotropies of favoured decays and the branching ratios of odd nuclei in the same mass region.

Fragmentation properties of 6Li

Abstract The α+d and t+τ cluster structure of 6Li is described in a microscopic α+d cluster model through quantities that enter into the description of cluster fragmentation processes. The states of the separate clusters α, d, t and τ are described as superpositions of 0s Slater determinants belonging to different potential size parameters. The model state space of 6Li is a tensor product of the α and d cluster state spaces and the state space of zero-orbital-momentum relative motion, restricted by antisymmetrization. To describe both the 6Li and fragment states realistically, we constructed nucleon-nucleon forces optimized for the model state spaces used. The fragmentation properties calculated are the g.s. fragmentation (or reduced-width) amplitudes, their squared Fourier transforms, the corresponding potential overlaps, the spectroscopic factors Sαd, Stτ and the αd asymptotic normalization constant C α d . The forces constructed reproduce the energies and charge radii of 6Li as well as of the fragments excellently. The fragmentation properties predicted by them slightly differ from those calculated with some forces of common use provided the latter are modified so as to reproduce the α, d and 6Li energies. The fragmentation properties change moderately in comparison with simpler versions of the cluster model. The full model yields S α d =0.93, S t τ =0.58 and C α d =3.3 . The results are consistent with phenomenological estimates except for C α d . The shape of our αd fragmentation amplitudes are in accord with α+p+n three-body calculations but our Sαd and C α d are substantially larger. We attribute this discrepancy to the neglect of the Pauli effects in the usual three-body formula for the αd fragmentation amplitude. We give a formula which contains the necessary remedy.

{alpha} Decay of Deformed Actinide Nuclei

{alpha} decay through a deformed potential barrier produces significant mixing of angular momenta when mapped from the nuclear interior to the outside. Using experimental branching ratios and either semiclassical or coupled-channels transmission matrices, we have found that there is a set of internal amplitudes which is essentially constant for all even-even actinide nuclei. These same amplitudes also give good results for the known anisotropic {alpha}-particle emission of the favored decays of odd nuclei in the same mass region. {copyright} {ital 1996 The American Physical Society.}

Theoretical description of superheavy nuclei

Abstract The theory of the superheavy elements is reviewed with the main focus on nuclear structure aspects. The structure of the odd- N superheavy elements is investigated using a variety of self-consistent approaches. Microscopic shell corrections, extracted from Skyrme–Hartree–Fock and relativistic mean-field calculations, elucidate the question of the centre-of-shell-stability in the superheavy region. Finally, the existence of exotic configurations, having gross non-uniformities of nucleonic density, expected to occur in nuclei with very large atomic numbers, is addressed.

Gamow and R-matrix approach to proton emitting nuclei

Proton emission from deformed nuclei is described within the nonadiabatic weak coupling model which takes into account the coupling to

PARTICLE-UNSTABLE NUCLEI IN THE HARTREE-FOCK THEORY

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Shell corrections for finite depth potentials: Particle continuum effects

vibrations around the axially symmetric shape. The coupled equations are derived within the Gamow state formalism. A new method, based on the combination of the