Gamow-Teller strength distributions for double-beta-decaying nuclei within continuum-QRPA

A version of the pn-continuum-QRPA is outlined and applied to describe the Gamow-Teller strength distributions for $\beta\beta$-decaying open-shell nuclei. The calculation results obtained for the pairs of nuclei $^{116}$Cd-Sn and $^{130}$Te-Xe are compared with available experimental data.Comment: 8 pages, 3 figures, To appear in the proceedings of "Nucleus-2007: Fundamental problems of nuclear physics, atomic power engineering and nuclear technologies" Voronezh, Russia, June 25-29, 200

Phosphorene nanoribbons

Edge-induced gap states in finite phosphorene layers are examined using analytical models and density functional theory. The nature of such gap states depends on the direction of the cut. Armchair nanoribbons are insulating, whereas nanoribbons cut in the perpendicular direction (with zigzag and cliff-type edges) are metallic, unless they undergo a reconstruction or distortion with cell doubling, which opens a gap. All stable nanoribbons with unsaturated edges have gap states that can be removed by hydrogen passivation. Armchair nanoribbon edge states decay exponentially with the distance to the edge and can be described by a nearly-free electron model

Sensitive behavior of 2νββ2\nu\beta\beta-decay amplitude within QRPA and broken SU(4) symmetry in nuclei

Making use of an identity transformation independent of a nuclear model, we represent the {\bb}-amplitude as a sum of two terms. One term accounts for most of the sensitivity of the original {\bb}-amplitude to $g'_{pp}$ for realistic $g'_{pp}\simeq 1$ (with $g'_{pp}$ being the ratio of the triplet and singlet p-p interaction strengths) and is determined by a specific energy-weighted sum rule. The sum rule depends only on the particle-particle residual interaction (being linear function of $g'_{pp}$ in the QRPA) and passes through zero at the point $g'_{pp}=1$ where the Wigner SU(4) symmetry is restored in the p-p sector of the Hamiltonian. The second term in the decomposition of the {\bb}-amplitude is demonstrated within the QRPA to be a much smoother function for the realistic values of $g'_{pp}$ than the original {\bb}-amplitude. This term is mainly determined by the intensity of the spin-orbit interaction of the nuclear mean field. Thus, the analysis of the present work reveals the reasons for the sensitivity of the {\bb}-amplitude to different components of the nuclear Hamiltonian and thereby can help in constraining nuclear model uncertainties in calculations of the amplitude.Comment: 14 pages, 3 figures; to be published in Nucl. Phys.