Alpha decay from deformed nuclei (original) (raw)

Α-Decay Spectroscopy of Deformed Nuclei Reexamined

Physical Review C, 2008

We perform an extensive analysis of α-decays to 2 + and 4 + states in deformed even-even nuclei by using the stationary coupled channels approach. Collective excitations are described within the rigid rotor model. The α-nucleus interaction is given by a double folding procedure with M3Y plus Coulomb nucleon-nucleon forces. We use a repulsive potential with one independent parameter in order to localize the α-particle on the nuclear surface and to fit the experimental Q-value. The decaying state is identified with the first resonance inside the resulting pocket-like potential, as suggested by microscopic calculations. We obtain a good agreement with existing experimental data concerning decay widths to J = 2 + , 4 + states. The total α-decay half-lives agrees very well with experimental values by fitting the spectroscopic factor in terms of charge and neutron numbers separately for Z < 82 and Z > 82. We give predictions for intensities and hindrance factors for 52 even-even α-emitters with β 2 > 0.15 and E 2 + < 200 kev. Comparison between the phenomenological and microscopic spectroscopic factors revealed large α-clustering components for nuclei close and above N = 82, Z = 82, N = 126 magic numbers.

Systematics of the α-decay to rotational states

Physical Review C, 2006

We analyze α decays to rotational states in even-even nuclei by using the stationary coupled channels approach. Collective excitations are described by the rigid rotator model. The α-nucleus interaction is given by a double folding procedure using M3Y plus Coulomb nucleon-nucleon forces. We use a harmonic oscillator repulsive potential with one independent parameter, to simulate the Pauli principle. The decaying state is identified with the first resonance inside the resulting pocketlike potential. The energy of the resonant state is adjusted to the experimental Q value by using the depth of the repulsion. We obtained a good agreement with existing experimental data concerning total half-lives and decay widths to J = 2 + states by changing the factor multiplying the nucleon-nucleon interaction according to the rule v a = 0.668 − 0.004 (A − 208). Concerning the decay widths to J = 4 + states we obtained a good agreement for Z = 90 neutron chain and a satisfactory description for Z = 92, 96, and 98, chains. It is possible to improve the agreement concerning transitions to J = 4 + states by considering a constant quenching strength v a = 0.6 and by changing the width of the Gaussian describing the α-cluster density according to the rule b = 1.744 − 0.032 (A − 208). We found out that the computed widths to excited states are correlated with the corresponding deformation parameters. We conclude that the α-decay fine structure is a sensitive tool to probe fundamental aspects of the effective nuclear interaction and its dependence on the α clustering.

Nuclear field theory approach to alpha-decay

Physics Letters B, 1979

The nuclear field theory is applied to the calculation of relative c~-decay rates in 212 At. All possible configurations are considered. The importance of collective states is discussed.

Penetration factor in deformed potentials: Application to α decay with deformed nuclei

A new averaging process of the calculation of α-decay half-lives for heavy and superheavy nuclei is studied in the framework of a deformed density-dependent cluster model. The potential between a spherical α particle and a deformed daughter nucleus is calculated numerically from the double-folding model by the multipole expansion method. The nuclear potential is calculated at each α-particle emission angle applying the Bohr-Sommerfeld condition at each case. The penetration factors and the half-lives for all the emission angles are evaluated with the new averaging process and compared with older values based on a fixed value of the nuclear potential depth. Finally, the half-lives of 83 even-even heavy nuclei in the atomic-number range 82-118 are calculated by the two methods and compared with their experimental values and the corresponding half-lives of the spherical daughter nuclei.

Relation of α-Decay Rotational Signatures to Nuclear Deformation Changes

Physical Review Letters, 1978

ABSTRACT It is shown that the rotational signatures for ground-band a decay can be calculated from nuclear (32 and (3 4 deformation values. The a-decay probability function over the nuclear surface is equated with the differences of the parent and daughter surfaces, hence with the changes in deformation parameters. It is suggested that deformation val­ues can be used to infer a wave functions at the nuclear surface for. a -transfer reaction theory on rotational signatures.

Effect of nuclear deformation on α-decay half-lives

Physical Review C, 2012

We systematically investigate the influence of nuclear deformations on the alpha-decay half-lives of the deformed medium, heavy and superheavy nuclei for 106 ≤ A ≤ 273 and 52 ≤ Z ≤ 110 from the ground state to ground state alpha transitions within the framework of the WKB method by considering the Bohr-Sommerfeld quantization condition. The deformed Wood-Saxon form in a phenomenological way and the deformed Coulomb potential in a special form have been used in order to take into account all deformation effects in the calculations and the preformation of the parent nuclei have also been regarded. Calculations have been conducted for the spherical nuclei in order to present clearly the effects of the deformations on the half-lives. We point out that all considerations have improved the results and very good agreement has been obtained with experimental data.

Microscopic description of the anisotropy in alpha decay

Physical Review C, 1994

A microscopic description of alpha decay of odd mass nuclei is given for axially deformed nuclei. Realistic mean field+pairing residual interaction in a very large single particle basis is used. Systematics for At and Rn isotopes, as well as for Fr, are given. A pronounced anisotropic emission of alpha particles at low temperatures is predicted as function of deformation for the At and Rn isotopes. This shows that alpha decay is an excellent tool to probe intrinsic deformations in nuclei.

Anisotropy in alpha decay of odd-mass deformed nuclei

Physical Review C, 1992

Angular distributions and the corresponding absolute a decay widths are calculated microscopically in odd axially deformed nuclei. It is found that the angular distributions are mainly determined by the deformation. The available experimental data are well reproduced.

Alpha decay as a probe for the structure of neutron-deficient nuclei

The advent of radioactive ion beam facilities and new detector technologies have opened up new possibilities to investigate the radioactive decays of highly unstable nuclei, in particular the proton emission, α decay and heavy cluster decays from neutron-deficient (or proton-rich) nuclei around the proton drip line. It turns out that these decay measurements can serve as a unique probe for studying the structure of the nuclei involved. On the theoretical side, the development in nuclear many-body theories and supercomputing facilities have also made it possible to simulate the nuclear clusterization and decays from a microscopic and consistent perspective. In this article we would like to review the current status of these structure and decay studies in heavy nuclei, regarding both experimental and theoretical opportunities. We then discuss in detail the recent progress in our understanding of the nuclear α formation probabilities in heavy nuclei and their indication on the underlying nuclear structure.

Double-beta decay in deformed nuclei

2002

The pseudo SU(3) approach has been used to describe many low-lying rotational bands, as well as BE(2) and B(M1) intensities in rare earth and actinide nuclei, both with even-even and odd-mass numbers [1, 2, 3, 4, 5, 6]. The ββ half lives of some of these parent nuclei to the ground and excited states of the daughter ones were evaluated for the two and zero neutrino emitting modes [7, 8, 9, 10, 11] using the pseudo SU(3) scheme. The predictions were in good agreement with the available experimental data for 150 Nd and 238 U. The double electron capture half-lives of 156 Dy, 162 Er and 168 Yb were also studied using the same formalism [12]. The first nuclei was found to be the best candidate for experimental detection, with a half-life of ≈ 10 24 yr to the first excited 0 + state in 156 Gd. There are strong selection rules which restrict the two neutrino mode of the ββ decay in some other nuclei, including 160 Gd. Experimental limits for the ββ decay of 160 Gd have been reported [13, 14]. Recently it was argued that the strong cancellation of the 2ν mode in the ββ decay of 160 Gd would suppress the background for the detection of the 0ν mode [15]. In the present contribution we extend the previous research [7, 8, 9, 10, 11] evaluating the ββ half lives of 160 Gd using the pseudo SU(3) model. While the 2ν mode is forbidden when the most probable occupations are considered, states with different occupation numbers can be mixed through the pairing interaction. The amount of this mixing is evaluated using perturbation theory. The possibility of observing the ββ decay in 160 Gd is discussed for both the 2ν and 0ν modes.