Remarks on monopole charge properties within the Generalized Coherent State Model

The Generalized Coherent State Model, proposed previously for a unified description of magnetic and electric collective properties of nuclear systems, is used to study the ground state band charge density as well as the E0 transitions from $0^+_{\beta}$ to $0^+_g$. The influence of the nuclear deformation and of angular momentum projection on the charge density is investigated. The monopole transition amplitude has been calculated for ten nuclei. The results are compared with some previous theoretical studies and with the available experimental data. Our results concerning angular momentum projection are consistent with those of previous microscopic calculations for the ground state density. The calculations for the E0 transitions agree quite well with the experimental data. Issues like how the shape transitions or shape coexistence are reflected in the $\rho(E0)$ behavior are also addressed.Comment: 32 pages, 7 figure

Angular correlation of electrons and positrons in internal pair conversion

The angular distribution of electrons and positrons emitted in internal pair conversion is calculated. Coulomb-distorted waves are used as electron wave functions. Nuclear transitions of various multipolarities L>0 and of magnetic (ML) and of electric (EL) type are considered as well as E0 conversion. Analytical expressions for the angular correlation are derived, which are evaluated numerically assuming a finite extension of the nucleus and, for the EL and ML conversion, also in the point-nucleus approximation. The calculated angular correlations are compared with results obtained within the Born approximation and, for the E0 case, with experimental data

Alternative Interpretation of Sharply Rising E0 Strengths in Transitional Regions

It is shown that strong 0+2 -> 0+1 E0 transitions provide a clear signature of phase transitional behavior in finite nuclei. Calculations using the IBA show that these transition strengths exhibit a dramatic and robust increase in spherical-deformed shape transition regions, that this rise matches well the existing data, that the predictions of these E0 transitions remain large in deformed nuclei, and that these properties are intrinsic to the way that collectivity and deformation develop through the phase transitional region in the model, arising from the specific d-boson coherence in the wave functions, and that they do not necessarily require the explicit mixing of normal and intruder configurations from different IBA spaces.Comment: 6 pages, 3 figure

Origin of the anomalous magnetic circular dichroism spectral shape in ferromagnetic (Ga,Mn)As: Impurity bands inside the band gap

The electronic structure of a prototype dilute magnetic semiconductor (DMS), Ga1-xMnxAs, is studied by magnetic circular dichroism (MCD) spectroscopy. We prove that the optical transitions originated from impurity bands cause the strong positive MCD background. The MCD signal due to the E0 transition from the valence band to the conduction band is negative indicating that the p-d exchange interactions between the p-carriers and d-spin is antiferromagnetic. The negative E0 MCD signal also indicates that the hole-doping of the valence band is not so large as previously assumed. The impurity bands seem to play important roles for the ferromagnetism of Ga1-xMnxAs.Comment: 13 pages, 3 figure