Microscopic description of the α-decay fine structure in spherical nuclei (original) (raw)
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The 0 + ↔ 0 − first-forbidden β decay transitions have been investigated for some spherical nuclei. The theoretical framework is based on a proton-neutron quasiparticle random phase approximation (pnQRPA). The Woods-Saxon potential basis has been used in our calculations. The transition probabilities have been calculated within the ξ approximation. The relativistic β moment matrix element has been calculated both directly without any assumption and assuming that it is proportional to the non-relativistic one.
Systematics of the α decay to vibrational2+states
Physical Review C, 2005
We give a systematic analysis of α decays to low-lying 2 + states in even-even nuclei. Collective excitations are considered within the spherical quasiparticle random-phase approximation. We use realistic G-matrix elements of the Bonn interaction as a residual two-body force. The only free parameters are the ratio between the isovector and isoscalar strengths and proton-neutron asymmetry. The formalism can reproduce the main experimental trends versus the excitation energy for both the B(E2) values and the α-decay hindrance factors. We reproduced most of the available data by using one common parametrization. It turns out that the fine structure of the α decay is more sensitive than electromagnetic transitions as a tool for investigating nuclear interaction. With the adopted parametrization, we predict B(E2) values and α-decay hindrance factors in even-even nuclei.
Physical Review C, 2008
We use the quasiparticle random-phase approximation (QRPA) and the Skyrme interactions SLy4 and SkM * to systematically calculate energies and transition strengths for the lowest 2 + state in spherical even-even nuclei. The SkM * functional, applied to 178 spherical nuclei between Z = 10 and 90, produces excitation energies that are on average 11% higher than experimental values, with residuals that fluctuate about the average by −35% to +55%. The predictions of SkM * and SLy4 have significant differences, in part because of differences in the calculated ground state deformations; SkM * performs better in both the average and dispersion of energies. Comparing the QRPA results with those of generator-coordinate-method (GCM) calculations, we find that the QRPA reproduces trends near closed shells better than the GCM, and that it overpredicts the energies less severely in general.
Calculation of the beta decay of . Quasiparticle random phase approximation results
Physics Letters B, 1992
Single beta decay transitions in l l4-12°pd are calculated. Theoretical 13 + and [I-strength distributions, for transitions to 1 + states in the nuclei 'l*-12°Ag and H a-12ORh ' are obtained in the framework of the quasiparticle random phase approximation (QRPA). The effective two-body interaction which is used in the calculations is constructed from the Bonn one-boson-exchange potential (OBEP). Particle-hole and particle-particle like channels of the two-body force are included in the definition of the QRPA matrix equations. Effects associated with the particle number violation of the quasiparticle mean field are accounted for by using a particle-number-projected version of the QRPA formalism. Theoretical strength distributions for the 13-and 13 + branches are shown and compared with data.
Α Decay as a Probe for Phase Transitions in Nuclei
Physical Review C, 1996
A microscopic description of alpha decay to intruder 0 2 ϩ states in the lead region is presented. The role played by proton-neutron correlations is emphasized. The calculated hindrance factors of transitions to the states 0 2 ϩ with respect to the corresponding ground state transitions are in good agreement with available experimental data. The abrupt variations in the measured hindrance factors in some cases are related to shape transitions. Predictions for further measurements are given. ͓S0556-2813͑96͒03509-1͔
Low-lying 2+ states in neutron-rich oxygen isotopes in quasiparticle random phase approximation
Physics Letters B, 2000
The properties of the low-lying, collective 2 + 1 states in neutron-rich oxygen isotopes are investigated in the framework of self-consistent microscopic models with effective Skyrme interactions. In RPA the excitation energies E 2 + 1 can be well described but the transition probabilities are much too small as compared to experiment. Pairing correlations are then accounted for by performing quasiparticle RPA calculations. This improves considerably the predictions of B(E2) values and it enables one to calculate more reliably the ratios M n /M p of neutron-to-proton transition amplitudes. A satisfactory agreement with the existing experimental values of M n /M p is obtained.
General behavior of double beta decay amplitudes in the quasiparticle random phase approximation
Physical Review C, 1993
Simple formulae for the 0 + → 0 + double beta decay matrix elements, as a function of the particle-particle strength g pp , have been designed within the quasiparticle random phase approximation. The 2ν amplitude is a bilinear function of g pp , and all 0ν moments behave as ratios of a linear function and the square root of another linear function of g pp. It is suggested that these results are of general validity and that any modifications of the nuclear hamiltonian or the configuration space cannot lead to a different functional dependence.
Proton decay from excited states in spherical nuclei
Journal of Physics G: Nuclear and Particle Physics, 1998
Based on a single particle model which describes the time evolution of the wave function during tunneling across a one dimensional potential barrier we study the proton decay of 208 Pb from excited states with non-vanishing angular momentum ℓ. Several quantities of interest in this process like the decay rate λ, the period of oscillation T osc , the transient time t tr , the tunneling time t tun and the average value of the proton packet position r av are computed and compared with the WKB results.
Fine structure of α decay in odd nuclei
Physical Review C, 2001
Using an α decay level scheme, the fine structure in odd nuclei is explained by taking into account the radial and rotational couplings between the unpaired valence nucleon and the core of the decaying system. It is shown that the experimental behavior of the α decay fine structure phenomenon is governed by the dynamical characteristics of the system.
The transition in finite nuclei
Nuclear Physics A, 2007
We perform a direct finite nucleus calculation of the partial width of a bound ∆ isobar decaying through the non-mesonic decay mode, ∆N → N N. This transition is modeled by the exchange of the long ranged π meson and the shorter ranged ρ meson. The contribution of this decay channel is found to be approximately 60 % of the decay width of the ∆ particle in free space. Considering the additional pionic decay mode, we conclude that the total decay width of a bound ∆ resonance in nuclei is of the order of 100 MeV and, consequently, no narrow ∆ nuclear states exist, contrary to recent claims in the literature. Our results are in complete agreement with microscopic many-body calculations and phenomenological approaches performed in nuclear matter.