Parameters of Isotope Shifts for 2s2p~(3,1)P_1→ 2s~(2 1)S_0 Transitions in Heavy Be-Like Ions

The field shift and mass shift parameters of the 2s2p~(3,1)P_1→ 2s~(2 1)S_0 transitions in Be-like ions(70 ≤ Z≤ 92)are calculated using the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods with the inclusion of the Breit interaction and the leading QED corrections. We find that the mass shift parameters of these two transitions do not change monotonously along the isoelectronic sequence in the high-Z range due to the relativistic nuclear recoil effects. A minimum value exists for the specific mass shift parameters around Z= 80, especially for the 2s2p~(3,1)P_1→ 2s~(2 1)S_0 transition. In addition, the field shifts and mass shifts of these two transitions are estimated using an empirical formula, and their contributions are compared along the isoelectronic sequence.     

Absolute Cross Sections for Near-Threshold Electron-Impact Excitation of the 2s^2S→2p^2P Transition of Li-Like C^3＋, N^4＋, and O^5＋ Ions

Excitation cross sections of 1s^22s ^2S1/2 → 1s^22p^2p1/2,3/2 transition among the fine-structure levels in Li-like C^3＋, N^4＋, and O^5＋ ions are calculated for energies of the near-threshold by using the relativistic distorted-wave program REIE06. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are studied in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. The results of the Li-like C^3＋ ion settle the discrepancy between several previous experiments by using the crossed-beams fluorescence method, in good agreement with the measurements of Savin et al. Moreover, the results in Li-like N^4＋, and O^5＋ ions are compared with the previous experiments, and a good agreement is obtained.     

Uncertainty evaluation of the isotope shift factors for 2s2p~(3,1)P_1~o–2s~2 ~1S_0 transitions in B Ⅱ

Accurate isotope shift factors of the 2s2p~(3,1)P_1~o–2s~2 ~1S_0 transitions in B II, obtained with the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods, are reported. We found a linear correlation relation between the mass shift factors and the energies for the transitions concerned, considering all-order electron correlations. This relation is important for estimating the uncertainty in the calculation of isotope shift factors. These atomic data can be used to extract the nuclear mean-square charge radii of the boron isotopes with halo structures or to resolve the high precise spectroscopy of B II in astronomical observation.     

EFFECT OF CONFIGURATION INTERACTION ON EXCITATION AUTOIONIZATION CROSS SECTIONS

The effect of configuration interaction (CI) on the theoretical calculation of autoionization cross section for Li-like ions are studied in detail by employing the distorted wave Born exchange approximation. We consider the 1s²2s→1s2s2p and 1s²2s→1s2s3p transitions for Cs³⁺ and Al¹⁰⁺ ions. These two transitions account for the largest excitation autoionization cross section. It is found that the CI has a significant effect on the calculated results. The effect becomes larger with increasing atomic number.     

Effects of electron correlation and the Breit interaction on one- and two-electron one-photon transitions in double K hole states of He-like ions(10 ≤ Z ≤ 47)

The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s^2 configurations of 11 selected He-like ions(10 ≤ Z ≤ 47) are calculated using the fully relativistic multi-configuration Dirac–Fock method(MCDF). An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of the electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon(TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of the He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.     

Temperature effect on emission lines and fluorescence lifetime of the ~4F_(3/2) state of Nd:YVO_4

By measuring the absorption and fluorescence spectra and the fluorescence lifetime of 4F3/2 state of Nd3+ ions in YVO4 (2 at.-%) crystal at different temperature, the effects of temperature on the spectra and the lifetime of F3/2 state have been investigated. As the temperature is increased, the line width of the 4F3/2 -4I11/2 transitions is found to increase and the spectral line toward the longer wavelength, which are duo to the ion-phonon interaction. The variation fluorescence lifetime of the 4F3/2 state of Nd:YVO4 is found to be anomalous in the measured range 8 - 300 K. It is about 81 us at room temperature and decreases to 30 us at 8 K. The experimental results are explained by ascribing to the thermal mixing between the two Stark levels of 4F3/2 state with different lifetime.     

Dispersion Characteristics of a New Slow-Wave Structure

The microwave excitation in a new slow-wave structure, i.e. the plasma-filled coaxial cylindrical dielectric-loaded cylindrical waveguide, is investigated by using the self-consistent linear field theory in considering the collision effect between electrons and ions in the plasma via the collision frequency term. The determinant dispersion equation of the beam-wave interaction with a complex value of angular frequency is derived. The effects of plasma collision frequency on the output frequency and the wave growth rate of the beam-wave interaction are calculated and discussed.     

Excitation Energies of 1s^2 ns （6 ≤ n ≤ 9） States for Lithium-Like Systems from Z = 11 to 20

The non-relativistic energies of 1s^2 ns (6 ≤ n ≤ 9) states for the lithium-like systems from Z = 11 to 20 are calculated by using a full-core-plus-correlation (FCPC) method. The relativistic and mass-polarization effects on the energy are calculated by the first-order perturbation corrections. The correction from the quantumelectrodynamics effect is also included using effective nuclear charge. Based on these results and the quantum defect theory, the quantum defects of 1s^2ns series for these ions, as a function of energy, are determined. The comparisons between the ionization potentials for 1s^2ns states (6 ≤ n ≤ 9) obtained by the FCPC method and the semi-empirical method are carried out. The results show that their agreement is very well and the energies of all discrete states (n ≥ 10) below the ionization threshold of this series for the ions can be predicted by using their quantum defects.     

Study of Σ~*-Δ Interactions

We study the Σ~*-Δ interaction in the chiral SU(3) quark model and in the extended chiral SU(3) quark model.In these two models,the short-range interaction mechanism are totally different,one is from the one-gluon exchange and another is from the vector meson exchange.The possible reasons of forming strangeness-1 bound states are given.Comparisons between the cases with and without quark exchange effect are made.The results show the quark exchange effect does give attractions to (Σ~*Δ)_(ST)=0 5/2 and (Σ~*Δ)_(ST)=3 1/2 systems,which means the special symmetry is important.Also,we make some analysis on chiral field effect,our results show that the σ exchange dominantly provides the attractive interaction for these two states.     

Energy Spectra,g Factors and Their Pressure—induced and ／or Thermal Shifts of SrTiO3：Cr^3＋ and SrTiO3：Mn^4＋ Ⅱ：Pressure Effects on Ground_State g Factor and Splittings of t2^32E and t2^34A2 of Sr

By using the wavefunctions obtained from diagonalizing the complete d^3 energy matrix at normal and various pressures,the g factor of the ground state of SrTiO3:Cr^3 and its pressure-induced shift have been microscopically calculated.Only by taking the local strains around Cr^3 in SrTiO3:Cr^3 (which are about twice the bulk ones)and corresponding P-χ dependence,can we obtain a good agreement etween the calculated result of pressure-induced shift of ground-state g factor and the experimental one.The physical origins of this pressure-induced shift have been explained.It is found that the change of Dq^-1 with pressure makes main contribution to the pressure-induced shift of ground-state g factor of SrTiO3:Cr^3 .By using the wavefunctions obtained from diagonalizing the complete d^3 energy matrix at normal pressure,the relevant matrix elements and accordingly strain-induced splittings of t2^32E and t2^34A2 of SrTiO3:Cr^3 have been calculated.The important results of Yc.Zc,Pc and Qc have also been evaluated.It is the admixtures of basic wavefunctions resulted from the spin-orbit interaction and /or Coulomb interaction and /or Kramers degeneracy that make the strain-induced splittings of the levels nonzero.It is found that there are nonvanishing matrix elements of operators T2ξ between wavefuncgtions with positive Ms and those with negative Ms′ and those with negative ms′,which have important effects on the strain-induced splittings of the levels.     

Spectroscope studies of YAlO_3: (Lu~(3 )Nd~(3 ))

An increase of the Nd~(3 ) doping concentration and an enhancement of the laser induced fluorescence in the single crystal of YAlO_3: (Lu~(3 ), Nd~(3 )) have been observed and are attributed to the size compensation effect. The low temperature (4.2K) fluorescence spectra indicate that the structure of the sharp lines arising from the radiative transitions of Nd~(3 ) ions is not changed by the existence of Lu~(3 ) ions, but the emission lines are inhomogeneously more broadened. Besides, it has been observed that the fluorescence due to the radiative transition from the Stark's sublevel R_2 of the metastable level ~4F_(3/2) to the sublevels Y_1 of the manifold ~4I_(11/2) decreases with decreasing temperature and the fluorescence arising from the transitions R_1→Y_1 is relatively increased. The experimental fact is qualitatively interpreted.     

Propagation and interaction of ion-acoustic solitary waves in a quantum electron-positron-ion plasma

This paper discusses the existence of ion-acoustic solitary waves and their interaction in a dense quantum electron-positron-ion plasma by using the quantum hydrodynamic equations.The extended Poincar’e-Lighthill-Kuo perturbation method is used to derive the Korteweg-de Vries equations for quantum ion-acoustic solitary waves in this plasma.The effects of the ratio of positrons to ions unperturbation number density p and the quantum diffraction parameter H e (H p) on the newly formed wave during interaction,and the phase shift of the colliding solitary waves are studied.It is found that the interaction between two solitary waves fits linear superposition principle and these plasma parameters have significantly influence on the newly formed wave and phase shift of the colliding solitary waves.The investigations should be useful for understanding the propagation and interaction of ion-acoustic solitary waves in dense astrophysical plasmas (such as white dwarfs) as well as in intense laser-solid matter interaction experiments.     

Effects of exchange interaction and spin-fluctuation on the magnetic and magneto-optic properties of NdF3

The exchange interaction between the electrons in the different magnetic ions and the spin-fluctuation of the magnetic ions exist in the paramagnetic media NdF3. The exchange interaction between the electrons in the different magnetic ions may be equivalent to an effective field Hin that is in direct proportion to the magnetization M. The spin-fluctuation of the magnetic ions leads the coefficient of the effective field to vary with temperature. The effective field is given as Hin = -（0.75 ＋ 0.22T） × 10^-5M in NdF3. When the secondary crystal field effect is taken into account, the magnetic susceptibility and Verdet constant are calculated for NdF3 by means of the effective field Hin and the applied field He. The calculated results are in agreement with the measured ones.     

Relationship measurement between ac-Stark shift of ~(40)Ca~+ clock transition and laser polarization direction

Ac-Stark shift of atom levels is caused by an ac-electromagnetic field. As an electromagnetic wave, laser light does induce ac-Stark shift. It is proved experimentally that if the light is linearly polarized, the dynamic polarizability changes with polarization direction. The polarization direction of the linearly-polarized laser is tuned by 720?, and the ac-Stark shifts of the 4S_(1/2),m=±1/2→3D_(5/2,m=±1/2) clock transitions in ~(40)Ca~+ are measured in steps of 10?. The frequency shifts change with laser polarization in a periodical manner and have values opposite to each other.     

Weak- and hyperfine-interaction-induced 1s2s ~1S_0→ 1s~2 ~1S_0 E1 transition rates of He-like ions

Weak- and hyperfine-interaction-induced 1s2s1S0→ 1s2 1S0E1 transition rates for the isoelectronic sequence of Helike ions have been calculated using the multi-configuration Dirac–Hartree–Fock(MCDHF) and relativistic configuration interaction methods. The results should be helpful for the future experimental investigations of parity non-conservation effects.     

Effects of a Weakly Interacting Light U Boson on Protoneutron Stars Including the Hyperon-Hyperon Interactions

In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the star maximum mass. The modification to the maximum mass by the U-boson with the strong YY interaction is larger than that with the weak YY interaction. The maximum mass of the protoneutron star is less sensitive to the U-boson than that of the neutron star. The inclusion of the U-boson narrows down the mass window for the hyperonized protoneutron stars. As g~2/μ~2 increases, the species of hyperons, which can appear in a stable protoneutron star decrease. The rotation frequency, the red shift, the momentum of inertia and the total neutrino fraction of PSR J1903-0327 are sensitive to the U-boson and change with g~2/μ~2 in an approximate linear trend. The possible way to constrain the coupling constants of the U-boson is discussed.     

Oscillator strengths for 2 ^2P-n ^2D transitions of lithium-like systems with Z=11 to 20

The dipole-length, velocity and acceleration absorption oscillator strengths for the 1s^22p－1s^2nd(3≤n≤9) transitions of the lithium-like systems with Z=11 to 20 are calculated using the energies and the multiconfiguration interaction wavefunctions obtained from a full core plus correlation method. The agreement between the f-values calculated from the length, velocity and acceleration formulae is excellent. Our results agree closely with the experimental data available in the literature. Combining these discrete oscillator strengths with the single-channel quantum defect theory, the discrete oscillator strengths for the transitions from 1s^22p state to highly excited states (n≥10) and the oscillator strength densities corresponding to the bound-free transitions are obtained.     

The mixed-spins 1/2 and 3/2 Blume—Capel model with a random crystal field

The random crystal field(RCF) effects are investigated on the phase diagrams of the mixed-spins 1/2 and 3/2 Blume-Capel(BC) model on the Bethe lattice.The bimodal random crystal field is assumed and the recursion relations are employed for the solution of the model.The system gives only the second-order phase transitions for all values of the crystal fields in the non-random bimodal distribution for given probability.The randomness does not change the order of the phase transitions for higher crystal field values,i.e.,it is always second-order,but it may introduce first-order phase transitions at lower negative crystal field values for the probability in the range about 0.20 and 0.45,which is only the second-order for the non-random case in this range.Thus our work claims that randomness may be used to induce first-order phase transitions at lower negative crystal field values at lower probabilities.     

Energy Levels of Highly Ionized Ar ⅩⅣ

With the Breit interaction and quantum electrodynamics corrections considered, relativistic configuration interaction calculations have been carried out in the extended optimal level scheme using multi-configuration Dirac-Fock wave functions on the 204 energy levels and electric dipole transitions of Ar ⅩⅣ. The results of electric dipole transitions are in good agreement with experiments. Among the energy levels calculated, the lowest 125 levels are in good agreement with available experimental and other theoretical ones, and the other 79 levels are new ones obtained by the present work. This wide range of atomic energy levels is useful in astrophysics and plasma physics.     

PLE spectra analysis of the sub-structure in the absorption spectra of CdSeS quantum dots

The semiconductor CdSeS quantum dots (QDs) embedded in glass are analysed by means of absorption spectra, photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra. The peaks of absorption spectra shift to lower energies with the size of QD increasing, which obviously shows a quantum-size effect. Using the PLE spectra, the physical origin of the lowest absorption peak is analysed. In PLE spectra, the lowest absorption peak can be deconvoluted into two peaks that stem from the transitions of 1S_3/2--1S_e and 2S_3/2--1S_e respectively. The measured energy difference between the two peaks is found to decrease with the size of QD increasing, which agrees well with the theoretical calculation for the two transitions. The luminescence peak of defect states is also analysed by PLE spectra. Two transitions are present in the PLE, which indicates that the transitions of 1S_3/2--1S_e and 2S_3/2--1S_e are responsible for the defect states luminescence.