Isotopic selection using nuclear spin induced electric dipole transitions

The nuclear spin induced electric dipole transitions $\text{6p}{}^2\text{(}\text{1}\text{2}\text{,}\text{1}\text{2}{}_0\text{?6p}\text{n}\text{s(}\text{1}\text{2}\text{,}\text{1}\text{2}\text{)}{}^0{}_0$ and $\text{6p}{}^2\text{(}\text{1}\text{2}\text{,}\text{1}\text{2}\text{)}{}_0\text{?6p}\text{n}\text{d}\text{1}\text{2}\text{[}\text{3}\text{2}\text{]}{}^0{}_2$ in ²⁰⁷Pb have been observed in the vacuum ultraviolet absorption spectrum of lead. Utilization of such transitions as a step in the laser isotope separation of ²⁰⁷Pb has the advantage that the selective pumping step involves levels which are separated by the relatively large fine structure spacing rather than the relatively small electronic isotopic and/or hyperfine spacings. The possibility of the separation of other odd mass numbered isotopes in the sixth and seventh periods by similar techniques is discussed briefly.     

Field-induced spin-flip and spin-flip transitions in PrGa2

A detailed neutron diffraction study of a single crystal of hexagonal PrGa₂ under an applied field is presented. The field is applied along the easy [100] direction of the hexagonal plane. The compound exhibits several field-induced magnetic structures and, in particular, an uncompensated long period commensurate antiphase structure defined by the propagation vector (4/27, 4/27, 0) at zero field and below T_t = 3.5 K. Concerning the intermediate magnetic structures below T_t, two types of magnetic phase transitions are observed: a spin-flip transition where one moment per magnetic cell turns over, and a spin-slip transition from the low field commensurate propagation vector (4/27, 4/27, 0) to another commensurate vector (1/7, 1/7, 0). Between T_t and T_N = 7.2 K, the structure becomes apmlitude-modulated with a propagation vector (0.148, 0.148, 0.023). Important and original magnetic domain effects are also observed due to the high degeneracy of the easy direction of the hexagonal plane in both T<T_t and T_t<T<T_N regions.     

New bound spin-flip transitions in n-InSb

Donor spin - flip transitions with ΔN = 0, ΔM = ?1, and Δλ = 1 are observed in InSb in high magnetic fields using an optically pumped far-infrared laser system. Variational calculations of the donor levels yielded good agreement with previously observed donor transitions energies. As regards the new spin - flip transitions reported in this work, the theoretical treatment has to be revised particularly for obtaining correct selection rules.     

Probabilities of radiative dipole transitions of parahelium in an electric field

Quadratic Stark corrections to the wave functions, matrix elements, and probabilities of transitions between the singlet states ¹ S ₀ and ¹ P ₁ of helium atoms are calculated. The coefficients of the polynomials that depend on the effective principal quantum number of the upper level v _f and that approximate the numerical values of the polarizabilities, the quadratic corrections to the wave functions, and the probabilities of transitions to highly excited Rydberg states with large v _f are determined. The results of calculations testify that the probabilities of all σ transitions n _i ¹ S ₀ → n _f ¹ P ₁ and π transitions to the states with n _f > n _i /2 are decreased with increasing electric field strength, except for the transition 2¹ S ₀ → 2¹ P ₁, whose probability increases both for σ and for π transitions.     

Damping of the giant spin-flip dipole and spin-flip quadrupole charge exchange modes in 90Zr

The damping of the giant spin-flip dipole (L=1, S=1, T=1, J^π=0⁻, 1⁻, 2⁻) and spin-flip quadrupole (L=2, S=1, T=1, J^π=1⁺, 2⁺, 3⁺) charge exchange resonances in ⁹⁰Zr is calculated in a microscopic nuclear structure model which includes both one-particle-one-hole (1p1h) and two-particle-two-hole (2p2h) configurations in a systematic way. It is shown that the coupling to 2p2h configurations gives rise to a strongly energy dependent spreading width which shifts a large fraction of transition strength to high excitation energies. The implications for the analysis of intermediate energy ⁹⁰Zr(p,n) data is discussed.     

A strong magnetic dipole excitation in 40Ca observed in high-resolution inelastic electron scattering and coherent spin-flip transitions due to ground-state correlations

An ususually strong magnetic dipole transition from the ground state to a state at Ex = 10.319 MeV in ⁴⁰Ca has been observed in high-resolution inelastic electron scattering, contrary to expectations from the pure independent particle shell model. The transition strength, however, can be accounted for by coherent spin-flip transitions due to strong ground-state correlations.     

Investigation of anomalousK,L andM shell conversion in electric dipole transitions

Anomalous experimental conversion coefficients of theK, L andM subshells are investigated for thirteen highly hindered electric dipole transition in six deformed odd mass nuclei. For a distinct nuclear transition, all experimental anomalies are consistent with one parameter, containing all nuclear information. The values of this parameter are determined and a simple connection with the hindrance of the transition seems to exist. TheK andL shell conversion coefficients have been recalculated, while theM shell conversion data were newly computed including all finite nuclear size effects as well as screening by a Thomas-Fermi-Dirac model.     

Low-Lying electric dipole transitions in tin isotopic chain within the RPA model

A nuclear structuremodel based on a finite rank approximation of Skyrme interaction is applied to calculate the distribution of dipole strength in tin isotopes. The model is based on the quasiparticle random phase approximation. The results obtained with the three types of parametrizations of the Skyrme forces (SLy4, SkM*, and SIII) are compared. The low-lying part of dipole strength distribution reveals the existence of a group of slightly collective states, and the corresponding E1 transition strength increases with the enlargement of neutron excess. The group is associated with the pygmy resonance. The text was submitted by the authors in English.     

Effect of metallic and hyperbolic metamaterial surfaces on electric and magnetic dipole emission transitions

Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial (HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental results obtained by measuring angular-dependent emission spectra of europium ions on top of different films. The results show the modified behavior of electric and magnetic dipoles on metallic and HMM surfaces. The results of numerical calculations agree well with experimental data.     

Resonant neutrino spin-flip transitions in twisting magnetic fields

We examine here in detail the dynamics of neutrino spin-flip transitions in twisting magnetic fields. The properties of various resonant conversions induced by field rotation are considered. The suppression factors for solarv _eL due to spin-flip transitions in twisting magnetic fields are calculated, and possible implications for solar neutrino experiments are discussed.     

Inner conversion process of electric dipole transitions in180Hf and182W

The conversion electron process of the retarded electric dipole transitions of 58keV in¹⁸⁰Hf and 67, 116, 152, 156 and 222 keV in¹⁸²W have been studied by means of high resolution double focusing beta-ray spectrometers. No penetration effects were found in the conversion process of the retarded 58 keV and 67, 116 and 222 keV E1 transitions. While the retarded 152 and 156 keV transitions in¹⁸²W show an anomalous internal conversion ratios compared with theoretical values. Implications of the results for current nuclear theories are discussed.     

Probabilities of electric dipole transitions in the spectra of ions of the erbium isoelectronic sequence

The probabilities of the 4f ¹³6p→4f ¹³ ns (n=6 and 7) electric dipole transitions are calculated for the spectra of YbIII, LuIV, and HfV ions of the erbium isoelectronic sequence. The wave functions of the intermediate coupling scheme, which are necessary for calculating the relative line strengths, are semiempirically obtained from experimentally measured energy intervals between the fine-structure levels. To pass to the absolute values, radial integrals of transitions are used, which are evaluated with the Hartree-Fock functions.     

A neutron electric dipole moment from supersymmetric QCD

Supersymmetric QCD naturally contains CP-violating interactions which can contribute to a neutron electric dipole moment. An analysis of the two-loop graphs results in a non-zero EDM whose magnitude is estimated and found to be compatible with experiment.     

A comment on the isovector dipole and Gamow-Teller transitions in 90Zr

It is suggested on the basis of transition strength and excitation energy arguments, that the resonance at 18.5 MeV observed in the ⁹⁰Zr(³He, t)⁹⁰Nb-experiment corresponds to a T=4 isovector dipole state.