A. Staudt

Second-generation microscopic predictions of beta-decay half-lives of neutron-rich nuclei

Abstract Beta-decay half-lives for neutron-rich nuclei with 6 ≤ Z ≤ 108 between the line of β-stability and the neutron drip line have been calculated in a second-generation microscopic calculation using the proton-neutron quasiparticle random-phase approximation (QRPA) with a Gamow-Teller residual interaction. The accuracy of the predictions is considerably improved over that of earlier approaches based on the gross theory and the Tamm-Dancoff approximation (TDA).

Microscopic Predictions of β+/EC-Decay Half-Lives

Beta-decay half-lives for β+/EC (electron capture) decay for neutron-deficient nuclei with atomic numbers Z = 10-108 have been calculated up to the proton drip line. For this purpose a proton-neutron quasiparticle random-phase approximation model (pn-QRPA) has been used. Both particle-hole and particle-particle residual interactions are taken into account. The calculated half-lives are in good agreement with experimental data, indicating the applicability of the model to the prediction of half-lives of unknown isotopes. The results of the present calculation are also compared to earlier theoretical work. It is shown that the pn-QRPA leads to considerable improvement over gross theory calculations.

Microscopic calculation of β+EC decay half-lives with atomic numbers Z = 10–30

Abstract By the use of the proton-neutron quasiparticle random-phase approximation, with both particle-hole and particle-particle residual interaction terms, we have calculated β + EC decay half-lives for isotopic chains with Z = 10–30 up to the proton drip line. The critical role of the particle-particle interaction in β + decay is discussed. By comparison of calculated half-lives with experimental data the good accuracy of the theoretical predictions is demonstrated.

Prediction of average β and γ energies and probabilities of β-delayed neutron emission in the region of fission products

Mean {beta} and {gamma} energies and probabilities of {beta}-delayed neutron emission (P{sub n}) in the region of fission products are calculated using a proton-neutron quasiparticle random-phase approximation nuclear model. {beta}-decay properties of these nuclides are essential input parameters for decay heat calculations for nuclear reactors. The results are compared with recent measurements. Mean energies and the P{sub n} values of {approximately}150 experimentally unknown short-lived isotopes are predicted.

Tensor force and operator expansion method for nuclear double beta decay

Abstract Using a general effective interaction containing σ . σ , τ . τ , σ . στ . τ and tensor terms, we have derived an approximate formula for calculating the M GT matrix element for nuclear 2 vββ decays. Our method is an extension of the operator expansion method of Ching and Ho which is for an effective interaction without tensor force. With the present formula the calculation of M GT does not require any information about the nuclear intermediate states, and our result is obtained without invoking closure approximation.

Nuclear matrix elements for double positron emission

Abstract Nuclear matrix elements for double positron emissions are calculated for both two-neutrino and zero-neutrino decay modes within the pnQRPA model with a realistic effective nucleon-nucleon interaction. This is the first complete microscopic calculation for all potential double positron emitters. The predicted lifetimes are several orders of magnitude larger than those for β−β− decays and difficult to reach in present days experiments.

Calculation of β-delayed fission rates of neutron-rich nuclei far off stability

Abstract Beta-delayed fission branching ratios P β df of heavy nuclides in the range 75 Z N ⩽ 184 are calculated using β-transition matrix elements determined in a pnQRPA approach. These P β df values are of great interest for the element synthesis in the astrophysical r-process. One of the main conclusions is that β-delayed fission prevents the synthesis of superheavy elements in nature by the r-process. Implications of the results on the yields of β-stable nuclides obtained in thermonuclear explosions are discussed.

Nuclear signatures in high-order harmonic generation from laser-driven muonic atoms

High-order harmonic generation from muonic atoms exposed to intense laser fields is considered. Our particular interest lies in effects arising from the finite nuclear mass and size. We numerically perform a fully quantum mechanical treatment of the muon-nucleus dynamics by employing modified soft-core and hard-core potentials. It is shown that the position of the high-energy cutoff of the harmonic spectrum depends on the nuclear mass, while the height of the spectral plateau is sensitive to the nuclear radius. We also demonstrate that gamma-ray harmonics can be generated from muonic atoms in ultrastrong VUV fields, which have potential to induce photonuclear reactions.

Simulation of atomic quantum dynamics in combined intense laser and weak electric fields

Numerical simulations are presented for a two-dimensional model of a hydrogen-like nitrogen ion in such intense laser fields that the electron velocity becomes non-negligible to that of light. With increasing laser field intensity, the role of its magnetic field component becomes more significant and a notable magnetically induced electron drift in laser propagation direction occurs. We show that this drift can be controlled to some degree by applying additional static or oscillating electric fields polarized in the laser propagation direction.

Stabilization of helium in intense high-frequency laser pulses beyond the dipole approximation

The stabilization dynamics of model He beyond the dipole approximation and with two active electrons is investigated in the presence of a high-intensity and high-frequency laser pulse. We show that the magnetic-field component of the laser pulse and the electron–electron interaction jointly suppress the dichotomy of the wavefunctions as well as the atomic stabilization.