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.     

Growth of high quality Ce~(3 ):YAP and (Ce~(3 ) Nd~(3 )): YAP single crystals

The effect of melt pretreatment of Ce~(3 ): YAP and (Ce~(3 ) Nd~(3 )): YAP and their growth ambient gases on the quality of the crystals are described. Firstly, a superheating pretreatment of YAP melt is adopted in a nitrogen atmosphere containing a little oxygen to eliminate carbon; then the YAP melt is superheated in a reduction atmosphere to fully reduce Ce~(4 ) ions into Ce~(3 ) ions in the melt. Finally, in a growth atmosphere of pure nitrogen, high quality Ce~(3 ): YAP and (Ce~(3 ) Nd~(3 )): YAP single crystals with high Ce~(3 ) concentration with only few light scattering centers were grown.     

Broken S_(3L)×S_(3R) flavor symmetry and leptonic CP violation

In the framework of the canonical seesaw model,we present a simple but viable scenario to explicitly break an S_(3L)×S_(3R) flavor symmetry in the leptonic sector.It turns out that the leptonic flavor mixing matrix is completely determined by the mass ratios of the charged leptons(i.e.,me/mμand mμ/mτ) and those of light neutrinos(i.e.,m_1/m_2 and m_2/m_3).The latest global-fit results of the three neutrino mixing angles {θ_(12),θ_(13),θ_(23)}and two neutrino mass-squared differences {?m_(21)~2,?m_(31)~2} at the 3σ level are used to constrain the parameter space of {m_1/m_2,m_2/m_3}.The predictions for the mass spectrum and flavor mixing are highlighted:(1) the neutrino mass spectrum shows a hierarchical pattern and a normal ordering,e.g.,m_1≈2.2meV,m_2≈8.8 meV and m_3≈52.7 meV;(2) only the first octant of θ_(23) is allowed,namely,41.8? θ_(23) 43.3?;(3) the Dirac C P-violating phase δ≈-22?deviates significantly from the maximal value-90?.All these predictions are ready to be tested in ongoing and forthcoming neutrino oscillation experiments.Moreover,we demonstrate that the cosmological matter-antimatter asymmetry can be explained via resonant leptogenesis,including the individual lepton-flavor effects.In our scenario,leptonic C P violation at low-and high-energy scales is closely connected.     

Crystal Structure and Judd–Ofelt Analysis of Er~(3+) Doped LuAl_3(BO_3)_4 Crystal

Single crystal Er:LuAl_3(BO_3)(Er:Lu AB) is successfully grown using the top-seeded solution growth method with a K_2Mo_3O_(10) flux. The cell parameters of the grown crystal are estimated by an x-ray single crystal diffactometor and x-ray powder diffraction analysis. The result indicates that it still belongs to the space group R32. The obtained unit-cell parameters are a= 9.2793(19) ?, c= 7.210(3) ?, V= 537.65(27) ?~3, and Z=3.The absorption spectrum is measured at room temperature. The spectroscopy properties are investigated based on the Judd–Ofelt(J-O) theory, and the effective J-O parameters were calculated to be Ω_2=8.33×10~(-20),Ω_4=3.83×10~(-20), and Ω_6 =3.55×10~(-20). The emission spectra of Er:LuAB crystal at room temperature are also studied and the ~4I_(11/2)→~4I_(13/2) fluorescence around 3170 nm is observed. The emission cross section calculated by the F-L formula is 8.6×10~(-20) cm~2. These results suggest that the Er:LuAB crystal may be a promising ~3 μm laser material.     

Double spin-glass-like behavior and antiferromagnetic superexchange interaction between Fe~(3+) ions in α-Ga_(2-x)Fe_xO_3(0≤x≤0.4)

Single phase of Fe3+-doped α-Ga2-xFexO3(α-GF x O, x = 0.1, 0.2, 0.3, 0.4) is synthesized by treating the β-Ga2-x Fe x O3(β-GF x O) precursors at high temperatures and high pressures. Rietveld refinements of the X-ray diffraction data show that the lattice constants increase monotonically with the increase of Fe3+content. Calorimetric measurements show that the temperature of the phase transition from α-GF x O to β-GF x O increases, while the associated enthalpy change decreases upon increasing Fe3+content. The optical energy gap deduced from the reflectance measurement is found to decrease monotonically with the increase in Fe3+content. From the measurements of magnetic field-dependent magnetization and temperature-dependent inverse molar susceptibility, we find that the superexchange interaction between Fe3+ions is antiferromagnetic. Remnant magnetization is observed in the Fe3+-doped α-GF x O and is attributed to the spin glass in the magnetic sublattice. At high Fe3+doping level(x = 0.4), two evident peaks are observed in the image part of the AC susceptibility χ ac. The frequency dependence in intensity of these two peaks as well as two spin freezing temperatures observed in the DC magnetization measurements of α-GF0.4O is suggested to be the behavior of two spin glasses.     

Structures of (ΩΩ)0 and (([1])Ω)1 in Extended Chiral SU(3) Quark Model

The structures of (ΩΩ)0 and (([1])Ω)1 are studied in the extended chiral SU(3) quark model in whichvector meson exchanges are included. The effect from the vector meson fields is very similar to that from the one-gluonexchange (OGE) interaction. Both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model,di-omega (ΩΩ)0 is always deeply bound, with over one hundred MeV binding energy, and (([1])Ω)1 ‘s binding energyis around 20 MeV. An analysis shows that the quark exchange effect plays a very important role for making di-omega(ΩΩ)0 deeply bound.     

The Electric-Field Controllable Non-Volatile 35° Rotation of Magnetic Easy Axis in Magnetoelectric CoFeB/(001)-Cut Pb(Mg_(1/3)Nb_(2/3))O_3-25%PbTiO_3 Heterostructure

Using in situ electric-field-modulated anisotropic magnetoresistance measurement,a large reversible and nonvolatile in-plane rotation of magnetic easy axis of ~35° between the positive and negative electrical poling states is demonstrated in Co_(40)Fe_(40)B_(20)/(001)-cut Pb(Mg_(1/3)Nb_(2/3))O_3-0.25PbTiO_3(PMN-PT).The specific magnetoelectric coupling mechanism therein is experimentaiiy verified to be related to the synchronous in-plane strain rotation induced by 109° ferroelastic domain switching in the(001)-cut PMN-PT substrate.     

Spin glassy behavior and large exchange bias effect in cubic perovskite Ba_(0.8)Sr_(0.2)FeO_(3-δ)

A single-phase iron oxideBa_(0.8)Sr_(0.2)FeO_(3-δ)with a simple cubic perovskite structure in Pm-3 m symmetry is successfully synthesized by a solid-state reaction method in O_2 flow. The oxygen content is determined to be about 2.81, indicating the formation of mixed Fe~(3+)and Fe~(4+)charge states with a disorder fashion. As a result, the compound shows small-polaron conductivity behavior, as well as spin glassy features arising from the competition between the ferromagnetic interaction and the antiferromagnetic interaction. Moreover, the competing interactions also give rise to a remarkable exchange bias effect in Ba_(0.8 )Sr_(0.2 )FeO_(2.81), providing an opportunity to use it in spin devices.     

Composite solitons in SU(3) spin–orbit-coupling Bose gases

We study solitons in a spin-1 Bose–Einstein condensates with SU(3) spin–orbit coupling. We obtain the ground state and the metastable solution for solitons with attractive interactions by the imaginary-time evolution method. Compared with the SU(2) spin–orbit coupling, it is found that the solitons in SU(3) spin–orbit coupling show a new feature due to breaking the symmetry. The solitons called the composite solitons have mixing manifolds of ferromagnetic and antiferromagnetic states. This has stimulated people to study the topological excitation properties of SU(3) spin–orbit coupling and it is expected to find new quantum phases.     

Photoluminescence properties of Y_(0.75-x)Gd_xAl_(0.10)BO_3:Eu_(0.10)~(3+),0.05R~(3+)(R= Sc,Bi) (0.00 ≤ x ≤ 0.45)

Y 0.75 -x Gd x Al 0.10 BO 3 :Eu0.10 3+, 0.05R 3+ (R=Sc, Bi) (0.00 ≤ x ≤ 0.45) powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y 3+ ions by Sc 3+ (or Bi 3+ ) and Gd 3+ ions in (Y,Al)BO 3 :Eu, the intensities of emission at 254 and 147 nm are remarkably improved, because Sc 3+ ions can absorb UV light and transfer the energy to Eu 3+ ions efficiently. Moreover, Gd 3+ and Bi 3+ ions act as an intermediate "bridge" between the sensitizer and the activator (Eu 3+ ) in energy transfer to produce light in the (Y, Gd)BO 3 :Bi 3+ , Eu 3+ system more effectively. After doping an appropriate concentration of Gd 3+ into Y 0.50 Gd 0.25 Al 0.10 BO 3 :Eu0.01 3+ , Bi0.05 3+ , the emission intensity reaches its maximum, which is nearly 110% compared with the red commercial phosphor (Y,Gd)BO 3 :Eu and better chromaticity coordinates (0.650, 0.350) are obtained.     

Fine structure and isotope shift of the 3s4d 3 D-3s3p 3 P, 3s5d 3 D-3s3p 3 P and 3p 2 3 P-3s3p 3 P Transitions of MgI

Summary We report the measurements of the³ D(3s4d)-³ P(3s3p)³ D(3s5d)-³ P(3s3p), and³ P(3p ²)-³ P(3s3p) transition frequency of MgI, the fine-structure separation and isotope shift between²⁴Mg and²⁶Mg. The measurements have been performed in a metastable atomic beam; a good agreement is found for data already existing in the literature. The accuracy of the measurements reported in this paper is mainly limited by the Doppler broadening of theI ₂ transitions used as a reference and by the precision in the knowledge of the related wavelengths.     

LaGaO3:RE3+(RE3+=Eu3+,Ho3+)的光谱

本文用固态反应合成了钙钛矿型的LaGaO3和LaGaO3:RE3+(RE3+=Eu3+,Ho3+)荧光体,并观察了物相随不同的激活离子浓度的变化。测量了化合物在室温下的反射光谱,激发光谱和荧光光谱。研究了Eu3+的D0→7F2和Ho3+的5S2→5I8的荧光强度与激活离子浓度的关系,发现了浓度猝灭,并得到了最大荧光强度的浓度值。     

The gas phase infrared band contours of s-triazine and s-triazine-d3: The fundamentals of C3N3H3 and C3N3D3 and some overtone and combination bands of C3N3H3

The systematic application of band contour techniques to account for most of the observed features of the ir spectra of s-triazine and s-triazine-d₃ have been made as well as a critique as to the limitations of such methods. The experimental and computer methods used to study the gas phase infrared band contours of s-triazine and s-triazine-d₃ are out-lined. Contours of the five E′ fundamentals of s-triazine have been recorded under moderate resolution and analyzed to give the Coriolis constants $\text{ζ}{}_{\mathrm{i}}{}^{\mathrm{z}}$, i = 6–10. The effects of l-resonance are very apparent for ν₈ and ν₉, in the form of holes in the Q branches of these bands. Under the highest resolution available, ν₆ and ν₁₀ also show l-resonance effects. Values of the l-doubling constants $\text{q}{}_{\mathrm{i}}{}^{\mathrm{(+)}}$ were obtained for these four fundamentals. One of the parallel A₂″ fundamentals of C₃H₃N₃ (ν₁₂) has also been studied. It lies close to ν₁₀(E′) and an A × E type of second-order Coriolis resonance may be the cause of the intensity enhancement observed in the inner wings of the ν₁₂ and ν₁₀ bands. Hot bands of the type (ν_i + nν₁₄ ? nν₁₄) have been observed in the contours of ν₈, ν₁₀, and ν₁₂. This is felt to be responsible for the large difference between our observed zeta sum (?1.30) and the theoretical sum (?1.00).The gas phase infrared band contours of the five E′ and 2A₂″ fundamentals of C₃N₃D₃ have also been recorded under moderate resolution. From P-R separations and by computer simulation of the contours, values of the Coriolis constants $\text{ζ}{}_{\mathrm{i}}{}^{\mathrm{z}}$ have been obtained for the E′ modes. The effects of l-resonance have been observed for ν₈(E′) and ν₁₀(E′) and values of the l-doubling constants $\text{q}{}_{\mathrm{i}}{}^{\mathrm{(+)}}$ have been estimated. An extensive series of hot bands of the type (ν₁₂ + nν₁₄ ? nν₁₄) has been observed in the contour of the ν₁₂ (A₂″) fundamental. The mass effect on the Coriolis constants has been discussed.Infrared band contours of the overtone 2ν₇ and seven degenerate E′ combination bands of C₃N₃H₃ have been recorded under moderate resolution. Analysis of these contours using the P-R separation method and computer simulation of the contours has given values of $\text{ζ}{}_{\mathrm{<mtext>eff</mtext>}}{}^{\mathrm{z}}$ for these bands. Fermi resonance between 2ν₇ and ν₆ has been analyzed. The importance of considering both the observed contour as well as the observed frequency when assigning higher tone bands is illustrated.     

Infrared spectra of matrix isolated BH3NH3, BD3ND3, and BH3ND3

The infrared spectra of ammonia-borane, BH₃NH₃, and two of its deuterated isotropic species, BD₃ND₃ and BH₃ND₃, isolated in argon matrix at liquid hydrogen temperature have been measured. Well resolved bands for these three isotopic species have been observed for all the fundamentals. A complete frequency assignment based on C₃v molecular symmetry has been made. A set of force constants have been calculated from the data for the two isotopes BH₃NH₃ and BD₃ND₃ using a valence force field. The agreement between experiment and frequencies calculated from these force constants for the mixed isotopic species, BH₃ND₃, substantiates the present assignment.     

Dielectric investigations of solid solutions SrTiO3-KTaO3 and SrTiO3-KNbO3

The temperature dependences of the dielectric constant and dielectric hysteresis loops in ceramic samples of (1 ? x)SrTiO_3?x KNbO₃ and (1 ? x)SrTiO_3?x KTaO₃ (0 ≤ x ≤ 0.3) solid solutions prepared using different heat treatments have been investigated. Phase diagrams of the studied solid solutions have been constructed in the T-x coordinates. It has been shown that, after quenching of samples (spontaneous cooling at room temperature after long-term heating at the sintering temperature of the ceramic samples), the temperature of the induced phase transition increases because of the weakening of random electric fields associated with nonisovalent impurities due to their “frozen” nonequilibrium redistribution. For small concentrations x, strong dielectric relaxation is observed in the temperature range of 150–250 K. A model of relaxing centers, which is based on the local charge compensation of heterovalent impurities, has been proposed.     

Modulated magnetic structures of ErPb3, HoPb3, ErTl3 and HoTl3

Neutron diffraction experiments have been carried out on the magnetically ordered phases of ErPb₃, HoPb₃, ErTl₃ and HoTl₃. The magnetic moments were found to be sinusoidally modulated with a propagation vector of (0, 0.2, 0.5) for the Pb-compounds and (0.38, 0.38, 0.16) for the Tl-compounds.Work supported by the Bundesministerium für Forschung und Technologie     

Ba3La(BO3)3基质中Tb3+的光致发光

以高温固相法合成了Ba3La(BO3)3∶Tb3 发光材料。在254nm紫外光激发下,研究了Ba3La(BO3)3∶Tb3 的激发光谱、发射光谱、发光强度与Tb3 浓度的关系。确定了Ba3La(BO3)3基质中Tb3 的自身浓度猝灭机理;探讨了助熔剂LiCO、敏化剂Ce3 、Bi3 的加入对荧光粉的发光强度的影响。     

Terahertz Vibrational Modes in CH3NH3PbI3 and CsPbI3 Perovskite Films

JETP Letters - Films of CH3NH3PbI3 organometallic perovskite, which is currently considered as a promising basic material for new-generation solar cells, as well as films containing CsPbI3...     

CH_3NH_3 Formed by Electron Injection at Heterojunction Inducing Peculiar Properties of CH_3NH_3PbI_3 Material

The effect of formed CH_3NH_3 at the heterojunction on properties of CH_3NH_3PbI_3 material is investigated based on experiment and theoretical calculation. Our calculation results show that the giant dielectric constant, anomalous hysteresis and long-lasting polarization for CH_3NH_3PbI_3 originate from the formed CH_3NH_3 at the heterojunction. It is found that the induced weak EPS by the reorientation of CH_3NH_3 sub-group along the built-in electric field enables us to effectively increase the ordering of entire lead-halide framework. In addition, the heterojunction has an advantage of channel separation between carrier transport and electron diffusion. These properties of the heterojunction are the main origin of the high efficiency of CH_3NH_3PbI_3 solar cells.