Half-lives $T_{1/2}^{2ν}$ for two neutrino positron double beta decay modes $β^{+}$EC/ECEC are calculated for $^{74}$Se, a nucleus of current experimental interest, using deformed shell model based on Hartree-Fock states employing a modified Kuo interaction in ($^{2}p_{3/2}$, $^{1}f_{5/2}$, $^{2}p_{1/2}$, $^{1}g_{9/2}$) space. The calculated half-life for the ECEC mode is $\sim 10^{26}$yr and it may be possible to observe this in the near future with improved sensitivity of experiments.
From the semi-empirical formalisms of Bohr-Mottelson, a new model, based on the effect of beta- and gamma- head energies and the variable moment of inertia, was developed to calculate the ground state rotational band of almost all deformed e-e nuclei. The model can be tuned for nuclei with experimentally available beta- and gamma-vibrational energies as well as for those with unmeasured beta- and gamma-vibrations.
Using deformed shell model based on Hartree-Fock intrinsic states with $^{70}$Zn as an example and employing two realistic effective interactions, namely jj44b that produces deformed shape and JUN45 that generates spherical shape, it is demonstrated that the $0ν$ and $2ν$ nuclear transition matrix elements for double beta decay will reduce considerably as we go from spherical shapes to deformed shapes. This result is further substantiated by using $^{150}$Nd as another example.
The 2 nu double beta decay half-lives of six nuclei, whose decays were previously reported as theoretically forbidden, are calculated by including the pairing interaction, which mixes different occupations and opens up the possibility of the decay. All allowed channels for the 0 nu double beta decay are also computed. The estimated 2 nu double beta half-lives suggest that measurements in 244Pu may find positive signals, and that planned experiments would succeed in detecting the 2 nu double beta decay in 160Gd. Limits for the zero neutrino mode, in the analyzed deformed emitters, are predicted…
The double beta decay of $^{100}Mo$ to the ground state and excited states of $^{100}Ru$ is analysed in the context of the pseudo SU(3) scheme. The results of this deformed limit are compared with the vibrational one based on the QRPA formalism. Consistency between the deformed limit and the experimental information is found for various $ββ$ transitions, although, in this approximation some energies and B(E2) intensities cannot reproduced.
We use a deformed QRPA formalism to describe simultaneously the energy distributions of the single beta Gamow-Teller strength and the two-neutrino double beta decay matrix elements. Calculations are performed in a series of double beta decay partners with A = 48, 76, 82, 96, 100, 116, 128, 130, 136 and 150, using deformed Woods-Saxon potentials and deformed Skyrme Hartree-Fock mean fields. The formalism includes a quasiparticle deformed basis and residual spin-isospin forces in the particle-hole and particle-particle channels. We discuss the sensitivity of the parent and daughter Gamow-Teller …
A selfconsistent approach based on a deformed HF+BCS+QRPA method with density-dependent Skyrme forces is used to describe beta+ decay properties in even-even deformed proton rich nuclei. Residual spin-isospin forces are included in the particle-hole and particle-particle channels. The quasiparticle basis contains neutron-neutron and proton-proton pairing correlations in the BCS approach, while neutron-proton pairing interaction is treated as a residual force in QRPA. We discuss the sensitivity of Gamow-Teller strength distributions and beta+/EC half-lives to deformation, pairing and the streng…
Using an angular momentum projected single particle basis, a pnQRPA approach is used to study the $2νββ$ properties of ten isotopes, exhibiting various quadrupole deformations. The mother and daughter nuclei exhibit different quadrupole deformations. Since the projected basis enables a unified description of deformed and spherical nuclei, situations where the nuclei involved in the double beta decay process are both spherical, both deformed or one spherical and another deformed, can be treated through a sole formalism. Dependence of single $β^-$ and $β^+$ strength distribution on atomic mass n…
We use the finite amplitude method for computing charge-changing Skyrme-QRPA transition strengths in axially-deformed nuclei together with a modern Skyrme energy-density functional to fit several previously unconstrained parameters in the charge-changing time-odd part of the functional. With the modified functional we then calculate rates of beta-minus decay for all medium-mass and heavy even-even nuclei between the valley of stability and the neutron drip line. We fit the Skyrme parameters to a limited set of beta-decay rates, a set of Gamow-Teller resonance energies, and a set of spin-dipole…
The two neutrino positron double beta decay of $^{106}$Cd for 0$^{+} \to $ 0$^{+}$ transition has been studied in the Hartree-Fock-Bogoliubov model in conjunction with the summation method. In the first step, the reliability of the intrinsic wave functions of $^{106}$Cd and $^{106}$Pd nuclei has been tested by comparing the theoretically calculated results for yrast spectra, reduced $B(E2$:$0^{+}\to 2^{+})$ transition probabilities, quadrupole moments $Q(2^{+})$ and gyromagnetic factors $g(2^{+})$ with the available experimental data. In the second step, the nuclear transition matrix element $…
A method to implement realistic nucleon-nucleon residual interaction (Bonn CD force) based on the Brueckner G-matrix into the Quasiparticle Random Phase Approximation (QRPA) for deformed nuclei is formulated. The two-neutrino double decay for ground state to ground state transitions $^{76}$Ge$ \to ^{76}$Se and $^{150}$Nd $\to ^{150}$Sm is calculated along with the Gamow-Teller strength distributions. The effect of deformation on the observables is studied.
The pseudo SU(3) approach is used to describe low lying states and BE(2) intensities of rare earth and actinide nuclei which are double beta decay candidates. The double beta half lives of some of these nuclei to the ground and excited states of the final ones are evaluated for both the two and zero neutrino emitting modes. The existence of selection rules which strongly restrict the decays is discussed. These restrictions represent a possible test of the model. Up to now the predictions are in good agreement with the available experimental data.
We use the axially-deformed Skyrme Quasiparticle Random-Phase Approximation (QRPA) together with the SkM* energy-density functional, both as originally presented and with the time-odd part adjusted to reproduce the Gamow-Teller resonance energy in 208Pb, to calculate the matrix elements governing the neutrinoless double-beta decay of 76Ge, 130Te, 136Xe, and 150Nd. Our matrix elements in 130Te and 136Xe are significantly smaller than those of previous QRPA calculations, primarily because of the difference in pairing or deformation between the initial and final nuclei. In 76Ge and 150Nd our resu…
We use the finite amplitude method (FAM), an efficient implementation of the quasiparticle random phase approximation, to compute beta-decay rates with Skyrme energy-density functionals for 3983 nuclei, essentially all the medium-mass and heavy isotopes on the neutron rich side of stability. We employ an extension of the FAM that treats odd-mass and odd-odd nuclear ground states in the equal filling approximation. Our rates are in reasonable agreement both with experimental data where available and with rates from other global calculations.
Beta-decay properties of even and odd-A neutron-rich Ge, Se, Kr, Sr, Ru, and Pd isotopes involved in the astrophysical rapid neutron capture process are studied within a deformed proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual interactions in the particle-hole and particle-particle channels are also included in the formalism. The isotopic evolution of the various nuclear equilibrium shapes and the corresponding charge radii are investigated in all…
The effect of deformation on the two-neutrino double decay (2nbb-decay) for ground state transition 76Ge -> 76Se is studied in the framework of the deformed QRPA with separable Gamow-Teller residual interaction. A new suppression mechanism of the 2nbb-decay matrix element based on the difference in deformations of the initial and final nuclei is included. An advantage of this suppression mechanism in comparison with that associated with ground state correlations is that it allows a simultaneous description of the single beta and the 2nbb-decay. By performing a detail calculation of the 2nbb-de…
In this work, we calculate the matrix elements of $0νββ$-decay of $^{150}$Nd with the deformed pn-QRPA method. We adopted the approach introduced by Rodin, Faessler [Phys. Rev. C84, 014322 (2011)] and Simkovic {\it et. al.} [Phys. Rev. C87,045501(2013)] to restore the isospin symmetry by enforcing $M^{2ν}_F=0$. We found that with this restoration, the Fermi matrix elements are reduced by about 30\% while the more important Gamow-Teller matrix elements remains the same. The results of an enlarged model space is also presented, which changes the matrix elements by less than 10\%.
In this paper a microscopic state-of-the-art approach to calculation of the nuclear matrix element $M^{0ν}$ for neutrinoless double beta decay with an account for nuclear deformation is presented in length and applied for $^{76}$Ge, $^{150}$Nd and $^{160}$Gd. The proton-neutron quasiparticle random phase approximation (QRPA) with a realistic residual interaction [the Brueckner $G$ matrix derived from the charge-depending Bonn (Bonn-CD) nucleon-nucleon potential] is used as the underlying nuclear structure model. The effects of the short range correlations and the quenching of the axial vector …
The zero neutrino mode of the double beta decay in heavy deformed nuclei is investigated in the framework of the pseudo SU(3) model, which has provided an accurate description of collective nuclear structure and predicted half-lives for the two neutrino mode in good agreement with experiments. In the case of $^{238}U$ the calculated zero neutrino half-life is at least three orders of magnitude greater than the two neutrino one, giving strong support of the identification of the radiochemically determined half-life as being the two neutrino double beta decay. For $^{150}Nd$ the zero neutrino ma…
After identifying the nuclei in the regions near A =80 and A = 160 for which beta-decay rates have the greatest effect on weak and main r-process abundance patterns, we apply the finite-amplitude method (FAM) with Skyrme energy-density functionals (EDFs) to calculate beta-decay half-lives of those nuclei in the quasiparticle random-phase approximation (QRPA). We use the equal filling approximation to extend our implementation of the charge-changing FAM, which incorporates pairing correlations and allows axially symmetric deformation, to odd-A and odd-odd nuclei. Within this framework we find d…
We describe and apply a version of the finite amplitude method for obtaining the charge-changing nuclear response in the quasiparticle random phase approximation. The method is suitable for calculating strength functions and beta-decay rates, both allowed and forbidden, in axially-deformed open-shell nuclei. We demonstrate the speed and versatility of the code through a preliminary examination of the effects of tensor terms in Skyrme functionals on beta decay in a set of spherical and deformed open-shell nuclei. Like the isoscalar pairing interaction, the tensor terms systematically increase a…
Beta-decay properties of neutron-rich Zr and Mo isotopes are investigated within a microscopic theoretical approach based on the proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual separable particle-hole and particle-particle forces are also included in the formalism. The structural evolution in these isotopic chains including both even and odd isotopes is analyzed in terms of the equilibrium deformed shapes. Gamow-Teller strength distributions, beta…
Four nuclei which are proved to be $2νββ$ emitters ($^{76}$Ge, $^{82}$Se, $^{150}$Nd, $^{238}$U), and four suspected, due to the corresponding Q-values, to have this property ($^{148}$Nd, $^{154}$Sm, $^{160}$Gd, $^{232}$Th), were treated within a proton-neutron quasiparticle random phase approximation (pnQRPA) with a projected spherical single particle basis. The advantage of the present procedure over the ones using a deformed Woods Saxon or Nilsson single particle basis is that the actual pnQRPA states have a definite angular momentum while all the others provide states having only K as a go…
Half-lives $T_{1/2}^{2ν}$ for two neutrino positron double beta decay modes $β^{+}$EC/ECEC are calculated for $^{84}$Sr, a nucleus of current experimental interest, within the framework of the deformed shell model based on Hartree-Fock states employing a modified Kuo interaction in ($^{2}p_{3/2}$, $^{1}f_{5/2}$, $^{2}p_{1/2}$, $^{1}g_{9/2}$) space. For a reasonable description of the spectra of $^{84}$Sr and $^{84}$Kr and to generate allowed GT strengths, the single particle energies of the proton and neutron $^1g_{9/2}$ orbitals, relative to the $^{2}p_{3/2}$ orbital energy, are chosen to be …
Symmetry restoration in the axially deformed proton-neutron quasiparticle random phase approximation for nuclear beta decay: The effect of angular-momentum projection
Sun Yat-sen University（中山大学）；University of North Carolina, Chapel Hill（北卡罗来纳大学教堂山分校）
Nuclear transition matrix elements (NTME) for the neutrinoless double beta decay of $^{70}$Zn, $^{80}$Se and $^{82}$Se nuclei are calculated within the framework of the deformed shell model based on Hartree-Fock states. For $^{70}$Zn, jj44b interaction in $^{2}p_{3/2}$, $^{1}f_{5/2}$, $^{2}p_{1/2}$ and $^{1}g_{9/2}$ space with $^{56}$Ni as the core is employed. However, for $^{80}$Se and $^{82}$Se nuclei, a modified Kuo interaction with the above core and model space are employed. Most of our calculations in this region were performed with this effective interaction. However, jj44b interaction…
We show that in a deformed ${\rm AdS}_5$ model with an explicit infrared cutoff included in the logarithmic correction $-c_0\log[(z_{IR}-z)/z_{IR}]$, the heavy quark Cornell potential can be fitted very well, the corresponding beta-function agrees with the QCD beta-function at 2-loop level reasonably well, and its dual dilaton potential is bounded from below in infrared. The results are compared with those in the Andreev-Zakharov model and the Pirner-Galow model.
Beta-decay properties of neutron-rich Ca, Ti, and Cr isotopes are studied within a deformed proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual spin-isospin interactions in the particle-hole and particle-particle channels are also included in the formalism. The energy distributions of the Gamow-Teller strength, the beta-decay feedings, the beta-decay half-lives, and the beta-delayed neutron emission probabilities are discussed and compared with other …
Spectroscopy of nuclei in the mass range A=76 to A=130, participating in double beta decay processes are studied in the framework of the self-consistent deformed Hartree-Fock (HF) and angular momentum (J) projection model. Spectra of ground bands have been studied and compared with available experimental results for even-even parent and daughter as well as for intermediate odd-odd nuclei. To test the reliability of the wave functions we have also calculated the reduced E2 transition matrix elements, electric quadrupole moments and magnetic dipole moments for these nuclei. The calculated result…
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 . The double beta 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 using the pseudo SU(3) scheme. The predictions were in good agreement with the available experimental data for 150Nd and 238U. The double electron capture half-lives of 156Dy, 162Er and 168Yb were also studied using the same f…
Positron-Emitting and Electron-Capturing Double-Beta Processes in the Standard Model and Beyond
Institute of Physics, Silesian University in Opava（俄帕瓦西里西亚大学物理研究所）；Finnish Institute for Educational Research, University of Jyväskylä（于韦斯屈莱大学芬兰教育研究所）；International Center for Advanced Training and Research in Physics (CIFRA)（国际高级物理培训与研究中心）；Department of Physics, University of California Berkeley（加州大学伯克利分校物理系）
Bulk and decay properties, including deformation energy curves, charge mean square radii, Gamow-Teller (GT) strength distributions, and beta-decay half-lives, are studied in neutron-deficient even-even and odd-A Hg and Pt isotopes. The nuclear structure is described microscopically from deformed quasiparticle random-phase approximation calculations with residual interactions in both particle-hole and particle-particle channels, performed on top of a self-consistent deformed quasiparticle Skyrme Hartree-Fock basis. The observed sensitivity of the, not yet measured, GT strength distributions to …
We revisit the computation of the phase space factors (PSF) involved in the positron decay and electron capture (EC) processes for a large number of nuclei of experimental interest. To obtain the electron/positron wave functions needed in computation, we develop a code for solving accurately the Dirac equation with a nuclear potential derived from a realistic proton density distribution in the nucleus. The finite nuclear size (FNS) and screening effects are included through recipes which differ from those used in previous calculations. Comparing our results with former calculations employing a…
We propose a consistent prescription for the derivation of the particle number and angular momentum projected QRPA (PQRPA) equation in the Generator Coordinate Method (GCM) framework for calculation of NME's of double-beta decay of axially deformed nuclei. We derive closed formulae for the calculation of excitation energies and wave functions of the intermediate nucleus.
Gamow-Teller strength distributions, beta-decay half-lives, and beta-delayed neutron emission are investigated in neutron-rich Zr and Mo isotopes within a deformed quasiparticle random-phase approximation. The approach is based on a self-consistent Skyrme Hartree-Fock mean field with pairing correlations and residual separable particle-hole and particle-particle forces. Comparison with recent measurements of half-lives stresses the important role that nuclear deformation plays in the description of beta-decay properties in this mass region.
Background: The major challenge for nuclear theory is to describe and predict global properties and collective modes of atomic nuclei. Of particular interest is the response of the nucleus to a time-dependent external field that impacts the low-energy multipole and beta-decay strength. Purpose: We propose a method to compute low-lying collective modes in deformed nuclei within the finite amplitude method (FAM) based on the quasiparticle random-phase approximation (QRPA). By using the analytic property of the response function, we find the QRPA amplitudes by computing the residua of the FAM amp…
We study the effect of deformation on the two-neutrino double beta decay for ground state to ground state transitions in all the nuclei whose half-lives have been measured. Our theoretical framework is a deformed QRPA based in Woods-Saxon or Hartree-Fock mean fields. We are able to reproduce at the same time the main characteristics of the two single beta branches, as well as the double beta matrix elements. We find a suppression of the double beta matrix element with respect to the spherical case when the parent and daughter nuclei have different deformations.
We identify here possible occurrence of large deformations in the neutron- and proton-rich regions of the nuclear chart from extensive predictions of the values of the reduced quadrupole transition probability B-E2 for the transition from the ground state to the first 2+ state and the corresponding excitation energy E2 of even-even nuclei in the recently developed Generalized Differential Equation model exclusively meant for these physical quantities. This is made possible from our analysis of the predicted values of these two physical quantities and the corresponding deformation parameters de…
We examine time reversal invariance in the beta-decays of 8B(2+) and 8Li(2+) to 8Be(2+) in detail, with particular attention to final state interactions of the two alpha particles from the decay of 8Be, and of the electron (positron) with the daughter nucleus. A R-matrix formulation is used, with the initial state described by a shell model. The R-matrix parameters are obtained by fitting the alpha-αscattering phase shifts and allowed beta-decay rates. Because the nuclear final state interaction effects on the time reversal test come from second forbidden beta-decays, they are small and can be…
We study lepton number violating (LNV) process of muon-positron conversion in nuclei mediated by the exchange of light and heavy Majorana neutrinos. Nuclear structure calculations have been carried out for the case of experimentally interesting nucleus 48Ti in the framework of renormalized proton-neutron Quasiparticle Random Phase Approximation. We demonstrate that the imaginary part of the amplitude of light Majorana neutrino exchange mechanism gives an appreciable contribution to the muon-positron conversion rate. This specific feature is absent in the allied case of neutrinoless double beta…
The two Gamow-Teller (GT) branches connecting the double-beta decay partners (116Cd, 116Sn) and (150Nd, 150Sm) with the intermediate nuclei 116In and 150Pm are studied within a microscopic approach based on a deformed proton-neutron quasiparticle random-phase approximation built on a Skyrme selfconsistent mean field with pairing correlations and spin-isospin residual forces. The results are compared with the experimental GT strength distributions extracted from charge-exchange reactions. Combining the two branches, the nuclear matrix elements for the two-neutrino double-beta decay are evaluate…
Gamow-Teller strength distributions and beta-decay half-lives in neutron-deficient Kr and Sr isotopes are investigated within a deformed quasiparticle random phase approximation. The approach is based on a selfconsistent Skyrme Hartree-Fock mean field with pairing correlations and residual separable particle-hole and particle-particle forces. A simple two-level model is used to mix the nuclear shapes into the physical ground state. Good agreement with experiment is found with shape mixing coefficients which are consistent with those obtained phenomenologically from mixing of rotational bands.
According to recent experimental data at GSI, the rates of the number of daughter ions, produced by the nuclear K-shell electron capture (EC) decays of the H-like ions 140Pr58+ and 142Pm60+, are modulated in time with periods T_(EC) simeq 7 s and amplitudes a_(EC) simeq 0.20. We study a possible time-dependence of the nuclear positron (beta^+) decay rate of the H-like 140Pr58+. We show that the time-dependence of the beta^+ decay rate of the H-like 140Pr58+ ion as well as any H-like heavy ions cannot be observed. This result can be used as a prediction for future analysis of the time-dependenc…
We study ground states and beta decay properties of the proton rich isotope chains Ge, Se, Kr, and Sr. We use a deformed selfconsistent HF+RPA approach with density-dependent effective interactions of Skyrme type. We find that most of the isotopes present two HF minima corresponding to two different shapes. In addition to static quadrupole moments and other ground state band properties, we present results for Gamow-Teller strength distributions, as well as for half-lives and summed strengths. The role of deformation is particularly emphasized.
The effect of nuclear deformation on the energy distributions of the Gamow-Teller strength is studied in neutron-deficient Hg, Pb, and Po even isotopes. The theoretical framework is based on a self-consistent deformed Skyrme Hartree-Fock mean field with pairing correlations between like nucleons in BCS approximation and residual spin-isospin interactions treated in the proton-neutron quasiparticle random phase approximation. After a systematic study of the Gamow-Teller strength distributions in the low excitation energy region, relevant for beta-decay, we have identified the best candidates to…
A theoretical approach based on a deformed quasiparticle random phase approximation built on a Skyrme selfconsistent mean field is used to describe the recent measurements of the Gamow-Teller GT- strength distribution extracted from the charge-exchange reaction 76Ge(3He,t)76As with high energy resolution. The same analysis is made to describe the Gamow-Teller GT+ strength distribution measured in the 76Se(d,2He)76As reaction. Combining these two branches, the nuclear matrix element for the two-neutrino double-beta decay process is evaluated and compared to experiment. The role of the nuclear d…
In this paper, beta-decay properties of even-even neutron-rich isotopes in the rare-earth mass region are studied within a microscopic theoretical approach based on a proton-neutron quasiparticle random-phase approximation. The underlying mean field is constructed selfconsistently from a deformed Hartree-Fock calculation with Skyrme interactions and pairing correlations to which particle-hole and particle-particle residual interactions are added. Nuclei in this mass region participate in the astrophysical rapid neutron capture process and are directly involved in the generation of the rare-ear…
Beta-decay properties of proton-rich odd-A and even-even Krypton isotopes are studied in the framework of a deformed selfconsistent Hartree-Fock calculation with density-dependent Skyrme forces, including pairing correlations between like nucleons in BCS approximation. Residual spin-isospin interactions are consistently included in the particle-hole and particle-particle channels and treated in Quasiparticle Random Phase Approximation. The similarities and differences in the treatment of even-even and odd-A nuclei are stressed. Comparison to available experimental information is done for Gamow…
A multi-shell generalization of a fermion representation of the q-deformed compact symplectic sp_q(4) algebra is introduced. An analytic form for the action of two or more generators of the Sp_q(4) symmetry on the basis states is determined and the result used to derive formulae for the overlap between number preserving states as well as for matrix elements of a model Hamiltonian. A second-order operator in the generators of Sp_q(4) is identified that is diagonal in the basis set and that reduces to the Casimir invariant of the sp(4) algebra in the non-deformed limit of the theory. The results…
The collective structure of atomic nuclei intermediate between spherical and quadrupole deformed structure presents challenges to theoretical understanding. However, models have recently been proposed in terms of potentials which are soft with respect to the quadrupole deformation variable beta. To test these models, information is needed on low-spin states of transitional nuclei. The present work involves measurement of electromagnetic decay properties of low-spin states for nuclei in the A=100 (gamma-soft) and N=90 (axially symmetric) transition regions. Population in beta-decay and thermal …
We study the properties of $^{74}$Kr, and particularly the Gamow Teller strength distribution, using a deformed selfconsistent HF+RPA method with Skyrme type interactions. Results are presented for two density-dependent effective two-body interactions, including the dependence on deformation of the HF energy that exhibits two minima at close energies and distant deformations, one prolate and one oblate. We study the role of deformation, residual interaction, pairing and RPA correlations on the Gamow Teller strength distribution. Results on moments of inertia and gyromagnetic factors, as well a…
Theoretical results for %the $0^{+}\to 0^{+}$ positron double-$β$ decay with emission of two neutrinos in the nuclei $^{96}$Ru, $^{102}$Pd, $^{106}$Cd and $^{108}$Cd are presented. The study employs the Hartree-Fock-Bogoliubov model to obtain the wave functions of the parent and daughter nuclei, in conjunction with the summation method to estimate the double beta decay nuclear matrix elements. The reliability of the intrinsic wave functions of $^{96,102}$Ru, $% ^{96}$Mo, $^{102,106,108}$Pd and $^{106,108}$Cd nuclei are tested by comparing the theoretically calculated spectroscopic properties w…
Background: To access selected excited states of nuclei, within the framework of nuclear density functional theory, the quasiparticle random phase approximation (QRPA) is commonly used. Purpose: We present a computationally efficient, fully self-consistent framework to compute the QRPA transition strength function of an arbitrary multipole operator in axially-deformed superfluid nuclei. Methods: The method is based on the finite amplitude method (FAM) QRPA, allowing fast iterative solution of QRPA equations. A numerical implementation of the FAM-QRPA solver module has been carried out for defo…
A theoretical analysis of the single-state dominance hypothesis for the two-neutrino double-beta decay rates is performed on the examples of the double-beta decays of 100Mo, 116Cd, and 128Te. We also test the validity of an extended low-lying-state dominance that takes into account the contributions of the low-lying excited states in the intermediate nucleus to the double-beta decay rates. This study has been accomplished for all the double-beta emitters for which we have experimental information on their half-lives. The theoretical framework is a proton-neutron quasiparticle random-phase appr…
We study the two-neutrino double-beta decay in 76Ge, 116Cd, 128Te, 130Te, and 150Nd, as well as the two Gamow-Teller branches that connect the double-beta decay partners with the states in the intermediate nuclei. We use a theoretical microscopic approach based on a deformed selfconsistent mean field with Skyrme interactions including pairing and spin-isospin residual forces, which are treated in a proton-neutron quasiparticle random-phase approximation. We compare our results for Gamow-Teller strength distributions with experimental information obtained from charge-exchange reactions. We also…
The nuclear K-shell electron-capture (EC)and positron (beta+) decay constants, lambda_(EC) and lambda_(beta^+) of H-like 140Pr58+ and He-like 140Pr57+ ions, measured recently in the ESR ion storage ring at GSI, were calculated using standard weak interaction theory. The calculated ratios R = lambda_(EC)/lambda_(beta^+) of the decay constants agree with the experimental values within an accuracy better than 3 %.
