Search

Europium-doped Y1−xGdxAlO3 perovskite (YAP) nanophosphors were synthesized by a solvothermal method. A YAP phase without impurity was formed from phosphors sintered at 1100 ° C. All the phosphors except YAlO3 can be estimated as mixed cubic and orthorhombic YAP phase. With the increase in Gd, the crystallinity was changed from simple cubic to q mixed phase of cubic and orthorhombic. Due to a 5D0→7F2 forced electric dipole transition of Eu3+, the nanophosphors with two mixed phases emitted radiation of red light with a 614 nm wavelength, whose brightness was dramatically increased by a factor 8 in comparison to that of the cubic perovskite phase. It is ascribed to the enhancement of non-symmetric environment for the Eu3+ in the nanophosphors with two mixed phases. The intensity ratios (IED/MD) between the structural hypersensitive force electric dipole transition, 5D0→7F2, and the intensity of the magnetic dipole transition, 5D0→7F1, are 0.4 for cubic phase and 1.4 for mixed phase.

A relativistic and non-Markovian study is carried out on the magnetic-dipole emission of a hydrogen-like atom of large atomic number Z without perturbation approximation. The correlation spectra are derived analytically and the corresponding correlation functions are calculated numerically. The Markovian approximation is seen to be satisfied with more accuracy as compared with the case of electric-dipole emission while the relativistic corrections are quite larger. In transition 2S1/2 to 1S1/2, the relativistic values even become several times of the non-relativistic values. As a comparison with the magnetic-dipole emission, the electric-quadrupole emission in the case of the 2D3/2 to 1S1/2 transition is also studied.

Magnetic dipole transitions between low-lying states in deformed even–even nuclei are studied in the framework of the neutron–proton interacting boson model. To obtain the nonvanishing M1 transitions between low-lying states, the proton–neutron quadrupole interaction is added to the dynamical symmetric SU(3) Hamiltonian as a perturbed term, which breaks F-spin symmetry. We introduce the expansion method which is similar to the intrinsic state formalism of the collective model to determine the matrix elements of SU(3) generators and apply first-order perturbation theory to derive M1 matrix elements between the perturbed states. Analytic forms for M1 transition rates between low-lying collective states are obtained and a comparison with available B(M1) ratios in 154Gd is presented.

The x-ray resonant scattering cross-section of K2ReCl6 has been studied for energies near the L edges of rhenium. Below the Neel temperature of TN ~ 11 K, additional peaks appear when the photon energy is tuned to the LII or LIII edges. The peaks are found to rotate the incident (linear) polarization, and have a Lorentzian lineshape in energy. The peaks are ascribed to resonant magnetic scattering, where a dipolar transition connects 2p–5d states. At resonance the scattering amplitude is of order ~ r0 per atom, roughly two orders of magnitude greater than that of the bare magnetic scattering.

We have calculated the forbidden transition energies and magnetic dipole transition probabilities of 2s22p4(3P1-3P2) and 2s22p4 (3P0-3P1) of oxygen-like isoelectronic sequences (Z=10-32) by a method of polarization potential correction. The transition energies show good agreement with experiment and are much better than the calculations in literature. These results also illustrate that it is feasible by using the dipole expansion of polarization potential to deal with some dynamic and non-dynamic effects in the central field approach. The relation of polarizability and cut-off radius with atomic number is discussed. We also give the fitted formula between the polarizability α1 and atomic number Z as α1=0.73429-9.56644×10-4Z+7.43016×10-5Z2 -2.53298×10-6Z3+2.08306×10-8Z4.

Electron-energy loss (EEL) is a successful tool to investigate inner-shell excitations of atoms and molecules1,2. In this technique a beam of energetic electrons is used to excite inner-shell transitions. The energy lost by the inelastically scattered electrons produces the excitation of the inner-shell state and the yield of the detected electrons provides information about the relative cross section for the excitation of the inner-shell state at that value of the incident energy. Then the dependence of the cross section from the momentum transfer in the collision can be studied by changing the scattering angle of the inelastically scattered electron. This latter characteristic together with the possibility to excite dipole forbidden transitions makes EEL a complementary technique to photoabsorption experiments. An important motivation for the study of inelastic collisions of electrons stems for the need of reliable cross section data in such diverse field as radiation physics, plasma physics, atmospheric physics, astrophysics and electron microscopy.

Two-colour two-photon detachment of via the magnetic dipole transition has yielded an accurate value for the fine-structure splitting of the ion: (0.620586(13) eV). The work clearly demonstrates the applicability of forbidden transitions in the study of the structure of negative ions. One-photon detachment from the level also provided a threshold value which, in combination with the well known binding energy, served as an independent measurement of the fine-structure splitting.

We report a measurement of parity non-conserving (PNC) optical rotation in the vicinity of the 1.279 magnetic dipole transition in atomic lead. We obtain a value for the conventional parameter, , with limits on the nuclear spin-dependent contribution set by the anapole constant . The experimental results, when combined with the relevant atomic calculations, lead to a value for the mass of the boson or, alternatively, place a limit on physics beyond the standard model through the isospin-conserving parameter, S.

Evidence for efficient non-radiative energy transfer between erbium ions in Cs2NaErCl6 is provided by excitation and luminescence spectra and luminescence lifetimes. In one of the cross relaxation schemes the excitation of the 4F3/2 level is transferred almost exclusively to the 4F9/2 level in the 50-300 K temperature region. The process of cross relaxation which removes the excitation from the 4S3/2 level is switched thermally at about 100 K and attains high efficiency at room temperature. Experimental results are interpreted using previously reported energies of normal vibrations of ErCl63- and the crystal-field levels of Cs2NaErCl6. It has been noted that virtually all efficient energy transfer schemes in Cs2NaLnCl6 reported thus far involve transitions between multiplets of the ground terms of lanthanides. All these transitions obey the selection rules for magnetic dipole transitions.

A description of the even-even Pt isotopes for A=188 to 198 in the framework of the neutron-proton interacting boson model is carried out. By introducing a triaxial interaction into the Hamiltonian, the gamma band is improved. The calculated spectra agree well with experimental data. E2 transitions agree with experimental data. The magnetic dipole transition is calculated and compared with the available data.

Two- and three-photon spectroscopy is very useful for the study of electronic properties of solids. After a rather general discussion of the “additional degrees of freedom” of these nonlinear techniques as compared to linear spectroscopy, the theoretical background of two-photon absorption and the polarization dependence for the special case of cubic symmetry are discussed. The polariton concept is briefly outlined. It is shown that the Maxwell boundary conditions have to be taken into account in the analysis of special cases in k-space spectroscopy. Several examples of two- and three-photon spectra in external fields will be presented. The effect of uniaxial stress and the Zeeman and Stark effect are studied in CuCl. As a further example experiments on two-photon magnetooptics of Landau levels in GaAs-AlGaAs multiple quantum wells are presented. Detailed information on experimental setups using nanosecond and picosecond tunable lasers will be given.

Polarised absorption and laser-induced fluorescence spectra of LiYF4:Eu3+ were recorded at liquid-nitrogen temperature in the visible spectral range. Transitions with pure electric dipole, pure magnetic dipole and mixed dipolar character have been observed. Spectroscopic assignments to the energy levels are made on the basis of the observed energies, polarisation characteristics of the spectral lines and electric and magnetic dipole selection rules relevant to the S4 point group. 37 Stark components belonging to ten multiplets of Eu3+ have been established. Free-ion and crystal-field parameters have been obtained. Simulation of the crystal-field energy levels has been attempted with and without J-J mixing effects using intermediate-coupling wavefunctions.

The optical absorption spectrum of Ho3+ in hexagonal (Ho0.1 Y0.9)(OH)3 was studied in the range from 15000 to 28000 cm-1 at temperatures between 1.4 and 50 K in magnetic fields up to 4 T. Fields along the crystal c axis were used to determine the splitting factors of the doublets. Fields perpendicular to c were applied to induce transitions from the lowest component of the ground term which are forbidden without field. The energies and the symmetry types of almost all crystal-field components could be established with great certainty.

We measured the radiative lifetime of the 1S0 metastable state of Kr2+. This state dominantly decays to the 3P1 state via a magnetic dipole transition. The lifetime was determined by measuring emitted photons (350.5 nm) as a result of the 1S0 → 3P1 decay of Kr2+ stored in an electrostatic ion trap. The obtained radiative lifetime was 15.3 ± 0.9 ms, which agrees with the experimental value reported by Calamai and Johnson (1992 Phys. Rev. A 45 7792) within experimental error.

Understanding and predicting the formation of shell structure from nuclear forces is a central challenge for nuclear physics. While the magic numbers N=2,8,20 are generally well understood, N=28 is the first standard magic number that is not reproduced in microscopic theories with two-nucleon forces. In this Letter, we show that three-nucleon forces give rise to repulsive interactions between two valence neutrons that are key to explain 48Ca as a magic nucleus, with a high 2+ excitation energy and a concentrated magnetic dipole transition strength. The repulsive three-nucleon mechanism improves the agreement with experimental binding energies., 5 pages, 4 figures; improved version and added coupled-cluster benchmark; published version

SnO2 nanocrystal and rare-earth Eu3+ ion co-doped SiO2 thin films are prepared by sol-gel and spin coating methods. The formation of tetragonal rutile structure SnO2 nanocrystals with a uniform distribution is confirmed by X-ray diffraction and transmission electron microscopy. Fourier transform infrared spectroscopy is used to investigate the densities of the hydroxyl groups, and it is found that the emission intensity from the 5D0−7F2 transitions of the Eu3+ ions is enhanced by two orders of magnitude due to energy transfer from the oxygen-vacancy-related defects of the SnO2 nanocrystals to nearby Eu3+ ions. The influences of the amounts of Sn and the post-annealing temperatures are systematically evaluated to further understand the mechanism of energy transfer. The luminescence intensity ratio of Eu3+ ions from electric dipole transition and magnetic dipole transition indicate the different probable locations of Eu3+ ions in the sol—gel thin film, which are further discussed based on temperature-dependent photoluminescence measurements.

The development of fusion reactors has generated a demand for improved knowledge of the atomic properties of tungsten. Using a multi-configuration Dirac–Fock (MCDF) method with a restricted active space treatment, the wavelengths and transition probabilities of the M1 and E2 transitions in the visible light region are calculated for the ground state multiplets of W26 + ions. The theoretical wavelength (388.43 nm) for the 3H5 → 3H4 magnetic dipole transition agrees quite well with the experimental value (389.41 nm). Other transitions theoretically predicted at longer wavelengths are also in good agreement with new experimental observations. The results also indicate that the core–core correlation contributions from the 4d shell are essential to determine the transition properties accurately.

The visible transition of a multiply charged Ba ion was observed by using an electron beam ion trap. From the dependence of the line intensity on electron beam energy, it is identified as a magnetic dipole transition between ground-state fine-structure levels (4d9 2D5/2–2D3/2) of Rh-like Ba. The wavelength determined from the present experiment is compared with the existing theoretical values as well as the indirect experimental value estimated from the wavelength difference between previously reported VUV transitions 4d85p–4d9 2D5/2 and 2D3/2.

Variational results of high accuracy are presented for electric quadrupole and magnetic dipole transitions between levels of the configurations 3pm, m = 2, 3, 4 for the ionized elements of Fe, Co and Ni. In each case, the accuracy of the wavefunction is evaluated by the agreement of the computed energy with observation and the agreement in the length and velocity form of the line strength for E2 transitions. It is shown that the line strength increases as more correlation effects are included and that semi-empirical methods may over-correct this increase. Transition rates computed from line strengths and observed transition energies result in lifetimes that decrease as more correlation is included in the wavefunction. Results are compared with other theory and experiment.

The probability W of the forbidden magnetic-dipole 21S0 — 23S1 transition in the helium atom is calculated to be 6.11×10-8 s-1. An estimate is obtained of the number of atoms excited to the 21S0 state by a travelling wave which is in resonance with the frequency of this transition.

Using the second order polarization propagator method we have calculated the band oscillator strengths of the "forbidden" Lyman-Birge-Hopfield band system, a1Πg ← X1Σg+, of N2 and the radiative lifetime τ(v') of the a1Πg state for 0 ≤ v' ≤ 4. We find that τ(0) = 58.6 μsec and τ(4) = 68.2 μs. About 95 per cent of the intensity are magnetic dipole contributions and only about 5 per cent come from the electric quadrupole radiation.

The 2p53s 1P1, 3P1–2p53p 1S0 transitions in Ne-like Ti XIII have been identified by beam-foil spectroscopy. The term value derived for the 3p1S0 level is used for improved predictions along the isoelectronic sequence by means of comparison with theoretical calculations. Accurate predictions of the magnetic dipole (M1) transition 2p53s 3P0–3P1 along the sequence are also made.

The 3p-3d transitions of the manganese-like ions Y14+, Zr15+, Nb16+, Mo17+, Ru20+, Rh21+ and Ag22+ have been studied in low inductance vacuum sparks. Isoelectronic regularities and theoretical calculations of wavelengths and line strengths supported the classification of 272 lines. The interpretation of 43 levels of 3d7 and 98 levels of 3p53d8 by means of the Slater-Condon theory led to fitted energy parameters in generalized least-squares procedures involving the 8 elements. Magnetic M1 dipole transitions within the ground configuration 3d7 are predicted for diagnostics in low density plasmas.

Making use of the computer program SUPERSTRUCTURE, radiative transition probabilities are calculated for forbidden lines in the ground configuration of O II. Elaborate procedures, such as configuration interaction, semi-empirical term energy corrections and radial wavefunctions produced by the computer program IMPACT, are used in the present calculation. In particular, the authors try to obtain an accurate theoretical value for the intensity ratior=I( lambda 3729)/I( lambda 3726). In nebulae where high electron densities are reached, this ratio tends to a value r( infinity ) which is determined by radiative transition probabilities. Astronomers have measured the ratio in nebulae for which the limit should be approached and have adopted for r( infinity ) a correct value of the order of 0.35. The best of the theoretical results reported here is 0.42, when the usual lowest order magnetic dipole transition operator, Q=L+2S, is included in the formalism. This does not improve on previous work. It is suggested that the persisting discrepancy is due to the neglect of higher order terms in the expression for the magnetic dipole operator, as shown by an encouraging first result.

We have measured parity-nonconserving optical rotation in the vicinity of the M1 absorption transition at 876 nm in bismuth. The result, R = Im(E1PNC/M1) = (-10.0 ± 1.0) 10-8, is in agreement with calculations based on the standard model of the electroweak interaction. The predicted form of the PNC rotation spectrum has been verified to high accuracy.

States in 130Ce have been studied using 16O induced reactions on 117Sn and 118Sn targets. Mean lifetimes have been measured for the yrast states up to Jπ = 22+ using both the Doppler shift attenuation and recoil distance methods. Magnetic dipole transition rates have been deduced from branching ratio measurements within a band based on an isomeric state at 2454 keV. Electric quadrupole transition rates have been determined from mean lifetime measurements for states in the yrast band up to Jπ = 22+. Both sets of results show an unexpected behaviour.

Electron paramagnetic resonance analysis of GaP:S samples has been performed under magnetic fields in the range 5 to 20 T. The spectra show a complex structure mainly dominated by an increase of the transmission coefficient near the expected magnetic resonance. Results are interpreted in terms of interference effects between levels of heteropolar pairs of neutral and ionized donors.

The observations of anomalous emission near the D1 transition of a dense (>or=1014 cm-3) sodium vapour illuminated by a laser detuned to the blue with respect to the D2 transition is studied and reported. A discussion of existing models is presented. The authors propose a type of parametric down-conversion process to explain this emission. This process involves a laser photon splitting into two photons by the three-level system of sodium, assisted by a magnetic dipole transition.

A procedure is developed by which M1 decay rates for a system with intermediate coupling can be computed from the corresponding rates in pure LS coupling and simple factors obtained from measured energy separations. Applications are made to the nsnp configurations in the Be, Mg and Zn isoelectronic sequences which are compared with ab initio MCDF calculations.

One of the major problems in using the interacting boson fermion model is its inability to predict magnetic dipole transition rates accurately. At least part of this problem is shown to be the neglect of quadrupole core-particle correlations. The effects of including such correlations are discussed with reference to the odd-even nuclei 107, 109Ag, 197Au and 103Rh.

The authors offer a solution to an old riddle. It concerns O II and electron density diagnostics in gaseous nebulae. Previous calculations of the high-density limit r( infinity ) for the line intensity ratio I(3729 AA)/(I(3729 AA) gave a low value well above the actually observed value of 0.35. The authors show that the magnetic dipole transition probability AM1(2D5/2 to 4S3/2) had been overestimated by a factor of four. Destructive interference with higher-order radiative terms drastically reduces the first-order transition amplitude. The other magnetic dipole transition probability involved, AM1(2D3/2 to 4S3/2), goes up by about 8%. Each effect lowers the calculated value for r( infinity ) by a similar amount. The results demonstrate that the ordinary magnetic dipole operator L+2S does not always yield a safe answer in intermediate-coupling calculations. A formulation that is consistent in powers of the fine-structure constant alpha requires relativistic terms in the operator; on its own such terms are familiar from lifetime calculations of the metastable level 1s2s 3S1 of He-like ions. The authors also show why the ordinary operator suffices in many cases of practical interest. Their calculations are based on configuration-mixing type expansions of the atomic wavefunctions.

The mean field of the 657 keV O+, T=1 level in 22Na for the radiative decay to the 583 keV 1+, T=0 level has been measured as tau =(27.1+or-1.2)ps. A modification of the recoil-distance method (RDM) was used. In addition, the mean life of the 891 keV level in the same nucleus was remeasured to give tau =(14.1+or-0.5)ps.

Calculations of the magnetic dipole M1 transition rates between 3P0 to 3P1 and 3P1 to 3P2 levels of 1s22s2p configuration in the beryllium isoelectronic sequence have been performed using the multiconfigurational Dirac-Fock extended average level (MCDF-EAL) method. Three nonrelativistic configurations 1s22s2, 1s22p2 and 1s22s2p are used. Breit and QED effects are treated as first-order perturbations. The role of the relativistic effects is crucial for the calculation of these transition rates. The transition rates between the magnetic fine-structure levels show a screened scaling behaviour. Experimental data are not available for comparison with the results.

This paper is an extension, to ions of higher charge, of an earlier paper which describes a collisional-radiative calculation for hydrogen-like ions of nuclear charge up to about 15. In the same way as before the authors take separate account of the (n,l,j) sub-levels up to n=4 and of each principal level up to n=50 assuming that the sub-levels within each of these principal levels are relatively statistically populated. Besides the usual radiative and electron collision processes they include heavy-ion (of any mass and charge) collisions among the sub-levels. In treating ions of nuclear charge greater than 15 it has been necessary (compared with the earlier paper) to modify the treatment of heavy-ion collisions, to include the possibility of radiative decay of the 2S metastable level by the magnetic dipole transition and to include the contribution of the helium-like satellite lines that lie close in wavelength to the individual components of the 1S-2P (Lyman-alpha) line. As before the authors concentrate on presenting the relative intensities of these two components. The present results show that it was justified to neglect the additional processes in the previous calculation.

The multi-configuration Hartree-Fock method, extended to include relativistic effects in the Breit-Pauli approximation (MCHF+BP), has been applied to the study of some forbidden transitions between levels of the 3s23p3 configuration in the phosphorus sequence. Term energy separations, fine-structure splittings, and E2 and M1 transition rates are reported for S II of interest in astrophysics and for several atomic systems with nuclear charge, Z, in the range 28

Parity non-conserving (PNC) optical rotation has been measured by laser polarimetry in the 648 nm magnetic dipole transition (6p3 J=3/2 to 6p3 J'=5/2) in atomic bismuth. The experiment involves finding the small differences in rotation between selected frequency points in the vicinity of the F=6 to F'=7 hyperfine component. Faraday rotation, which can be distinguished from PNC rotation by its wavelength dependence, is used in locking the laser frequency and calibrating the PNC effect. Results obtained over a six-year period are summarised; a detailed discussion of error sources and associated tests is given. The final result for the PNC parameter of the 648 nm transition is R=(-9.3+or-1.4)*10-8. This is an agreement with the measurements of Birich et al (1984) but not with those of Barkov and Zolotorev (1980). It is also consistent with the standard model of the electroweak interaction, but the uncertainty in the atomic theory is now the limiting factor in the comparison.

Spectral lines emitted from the different ionization stages of various elements present (either naturally occuring or deliberately added) in high-temperature tokamak plasmas may be used for localized diagnostics of such plasmas. This fact has motivated a search for transitions suitable for these purposes. Such transitions are of essentially two types: Δn = 0 resonance transitions (in particular of one- and two-valence electron systems) and magnetic dipole transitions arising within the ground configurations of ions of highly-ionized, high-Z elements. The latter transitions are peculiar to the fairly low-density, quasisteady plasmas prevailing in tokamaks – and to celestial plasmas. In this paper we review the progress that has been made in the line identification program, paying particular attention to the high-Z members of the isoelectronic sequences of the second period. For these sequences, critical examinations of measured data and comparisons with theoretical calculations have been carried out by Professor Bengt Edlen, resulting in highly accurate wavelength predictions.

The multiconfiguration Hartree-Fock method extended to include relativistic effects in the Breit-Pauli approximation (MCHF-BP) is tested in the study of the ground configuration of nitrogen-like ions. Fine-structure splittings, E2 and M1 transition rates calculated with the classical (nonrelativistic) form of the magnetic transition operator are presented and compared with other theoretical and experimental results up to Zn XXIV. The astrophysical problem of the high-density limit of the intensity ratio I(2D5/2 to 4S3/2)/I(2D3/2 to 4S3/2) is discussed on the basis of these new theoretical data.

The nuclear shell-model and the theory of fractional parentage are used to derive theoretical formulae for certain observable features of nuclear energy levels that are not expected to be sensitive to the choice of the nucleon interaction potential. These features comprise: (i) the magnetic dipole transition strengths, (ii) the magnetic moments, (iii) the reduced widths for nucleon emission. Intermediate coupling, besides extreme L-S and extreme j-j coupling, is discussed, and the resulting formulae are applied to the low-lying odd-parity states of 13C and 13N in an attempt to explain all the relevant experimental data. It is found that the extreme coupling models give generally poor agreement of theory with experiment. On the other hand, all the data are consistent with an intermediate coupling model and quite a small range of values of the intermediate coupling parameter.

A spectrum line observed at 3834.4 +- 0.2 A and identified as a 2s/sup 2/2p/sup 2/ /sup 3/P/sub 2/ ..-->.. /sup 3/P/sub 1/ magnetic dipole transition in the TiXVII ground configuration, was used for titanium density measurements in the Poloidal Divertor Experiment (PDX).

The possibility of the existence of a magnetic dipole transition with change in orbital angular momentum l of ±2 and its effect on the classification of the forbidden transitions in x-ray spectra has been pointed out.

For the purpose of evaluating the electric dipole and the magnetic dipole transition prababilities in Tb3+, the reduced matrix elements for 5 D 4→7 F J and 5 D 3→7 F J have been calculated. From the results, fluorescence colors producible by Tb3+-activated phosphors have been predicted: The best green colors with short persistence have the chromaticity coordinates around x=0.321, and y=0.651. For this purpose, Tb3+ ions should be embedded in lattice sites without inversion symmetry. The nonradiative transition probabilities for 5 D 3→5 D 4 due to multipolar interactions have been evaluated. When the Tb concentration is higher than several per cent, the quadrupole-dipole interaction between the Tb3+ ions in the metastable state 5 D 3 and those in the ground state 7 F 6 is predominantly responsible for the nonradiative 5 D 3→5 D 4 relaxation.