Synthesis and Structural Study of Sr2CuO3+δ Superconductor under High Pressure

A single-phase Sr₂CuO_3+δ superconductor is synthesized under high temperature and high pressure, in which oxygen atoms only partially occupy the apical sites next to the CuO₂ planes and act as hole-dopants. Thesuperconducting transition temperature with T_c^max=75K is achieved in the material. Structure analysis from x-ray powder diffraction data show that this material crystallizes into a K₂NiF₄ structure with tetragonal unit cell of a=3.795(3)AAand c= 12.507(1)AA. Energy-dispersive synchrotron x-ray-diffraction studies at ambient are performed on powder samples of Sr₂CuO_3+δ in a diamond-anvil cell at pressure up to 35GPa. Anisotropic compressibility is found. Pressure-induced isostructural phase transition might exist as revealed by the discontinuous change of crystal cell volume V withpressure.     

Stereodynamics of the O（3P） with H2（D2） （ν=0,j=0） reaction

Quasi-classical trajectory theory is used to study the reaction of O(3 P) with H 2 (D 2) based on the ground 3 A″ potential energy surface (PES).The reaction cross section of the reaction O+H 2 →OH+H is in excellent agreement with the previous result.Vector correlations,product rotational alignment parameters P 2 (j · k) and several polarizeddependent differential cross sections are further calculated for the reaction.The product polarization distribution exhibits different characteristics that can be ascribed to different motion paths on the PES,arising from various collision energies or mass factors.     

Pressure broadening coefficients of transitions in the ν5 band of methyl bromide from fitting to Voigt and Galatry line profiles

Tuneable diode laser absorption spectroscopy has been used to measure the room temperature pressure broadening coefficients (γ) of rotational transitions in the v₅ fundamental band of methyl bromide (¹²CH₃⁷⁹Br and ¹²CH₃⁸¹Br) around 6.9 μm. Nitrogen, oxygen and self-broadening coefficients have been determined for 125 lines in the ^RQ₁, ^PQ₃, ^PQ₅, ^PQ₇ and ^PQ₈ branches and 49 P and R branch transitions. Line profiles within Q branches were recorded at incremental pressures of nitrogen and oxygen up to 15 Torr and fitted to a Voigt profile to yield the broadening coefficients. The nitrogen broadened data for 14 lines, chosen from the five Q branches, were also fitted with Galatry profiles. The line profiles of the P and R branch transitions were recorded for total nitrogen and oxygen pressures of up to 300 Torr and fitted to both Voigt and Galatry profiles. Within individual Q branches, nitrogen broadening coefficients were found to decrease monotonically with increasing J from 0.14 cm⁻¹ atm⁻¹ at low J to 0.09 cm⁻¹ atm⁻¹ at high J. The corresponding values for oxygen were approximately 25% smaller. Self-broadening coefficients were found to vary between 0.48 and 0.16 cm⁻¹ atm⁻¹ with a similar J dependence to the foreign gas broadening for J > 20. However, between J = 2 and J ≈ 20 the broadening coefficient was found to increase with J. The magnitude of the pressure broadening coefficient for P and R branch transitions was found to closely follow the J dependence measured for the Q branch lines.     

Analysis of B → a1（1260）（b1（1235））K decays in the perturbative QCD approach

Within the framework of the perturbative quantum chromodynamics（PQCD） approach, we study the charmless two-body decays B → a₁（1260）K*, b₁（1235）K*. Using the decay constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results.（a） Our predictions for the branching ratios are consistent with the QCD factorization（QCDF） results within errors, but much larger than the naive factorization approach calculation values.（b） We predict that the anomalous polarizations occurring in the decays B→φK*, ρK*also happen in B→a₁ K*decays, while they do not happen in B→b₁ K*decays. Here the contributions from the annihilation diagrams play an important role in explaining the larger transverse polarizations in the B→a₁ K*decays, while they are not sensitive to the polarizations for the B→b₁ K*decays.（c） Our predictions for the direct C P-asymmetries agree well with the QCDF results within errors. The decaysˉB⁰→b₁₊K*-, B-→b₁⁰K*-have larger direct C P-asymmetries, which could be measured by the present LHCb experiment and the forthcoming Super-B experiment.     

First-principles study of electronic properties and stability of Nb5SiB2（001） surface

The density functional calculations are performed to study the electronic structure and stability of Nb 5 SiB 2(001) surface with different terminations.The calculated cleavage energies along the(001) planes in Nb 5 SiB 2 are 5.015 J · m 2 and 6.593 J · m 2 with the break of Nb-Si and Nb-NbB bonds,respectively.There exists a close correlation between the surface relaxation including surface ripple and the cleavage energy:the larger the cleavage energy,the larger the surface relaxation.Moreover,the surface stability of the Nb 5 SiB 2(001) with different terminations has been investigated by the chemical potential phase diagram.From a thermodynamics point of view,the four terminations can be stabilized under different conditions.In chemical potential space,NbB(Nb) and Nb(Si) terminations are just stable in a small area,whereas Si(Nb) and Nb(NbB) terminations are stable in a large area(the letters in brackets represent the subsurface atoms).     

The ν5 band of CH3CH3: High resolution stimulated Raman spectrum and global three band analysis

Rotationally resolved spectrum of ¹²CH₃¹³CH₃ in the region of ν₅ vibrational fundamental (CC stretch) was observed using stimulated Raman spectroscopy. This spectrum was analyzed with data from the ν₁₂ fundamental and transitions from the ν₆, 2ν₆-ν₆, and 3ν₆ torsional bands using a 3-state fit. One torsional component of the ν₅ fundamental is perturbed, interacting with its partner in the ν₆=4 of the torsional stack of the ground vibrational state. As for normal ethane, the coupling was successfully modeled using a Fermi-type interaction. The results mirror that of ¹²CH₃¹²CH₃ in that the inclusion of the Fermi-type interaction reduces the required number of terms in the Fourier expansion of the torsional potential for the ground vibrational state from three (in the 2-state fit) to one, only the term in the barrier height is required.     

Lattice potential energy and standard molar enthalpy in the formation of 1-dodecylamine hydrobromide (1-C12H25NH3 ·Br)（s）

This paper reports that 1-dodecylamine hydrobromide (1--C₁₂H₂₅NH₃·Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1--C₁₂H₂₅NH₃·Br and the ionic volume and radius of the 1--C₁₂H₂₅NH₃⁺ cation are obtained from the crystallographic data and other auxiliary thermodynamic data. The constant-volume energy of combustion of 1--C₁₂H₂₅NH₃·Br(s) is measured to be Δ_c U_m^o(1--C₁₂H₂₅NH₃·Br, s) =--(7369.03±3.28) kJ·mol^-1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T=(298.15±0.001) K. The standard molar enthalpy of combustion of the compound is derived to be Δ_c H_m^o(1--C₁₂H₂₅NH₃·Br, s)=--(7384.52±3.28) kJ·mol ^{- 1} from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be Δ_f H_m^o(1--C₁₂H₂₅NH₃·Br, s)=--(1317.86±3.67) kJ·mol^-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.     

Doping effects on structural and magnetic evolutions of orthoferrite SmFe（1-x） Alx O3

The structural and magnetic properties of SmFeO3 with B site substitution of non-magnetic atom A1 are investigated. The x-ray diffraction patterns show that SmFe（1-x）AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped A1 concentration. Besides, the octa- hedral tilting distortions of FeO6 are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard＇s rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 〈 x 〈 0.6, the ferromagnetism, antiferromagnetism, and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature （Tk） decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior.     

High sensitivity gravimetric sensor made of unidirectional carbon fiber epoxy composite on （1-x）Pb(Zn1/3Nb2/3)O3-xPbTiO3 single crystal substrate

We have derived a general formula for sensitivity optimization of gravimetric sensors and have used it to design a high sensitivity gravimetric sensor using unidirectional carbon fiber epoxy composite(CFEC) waveguide layer on(1- x)Pb(Zn1/3Nb2/3)O3-xPbTiO3(PZN-xPT) single crystal substrate with the carbon fibers parallel to the x1 and x2axes, respectively. The normalized maximum sensitivity Sfm λ maxexhibits an increasing tendency with the decrease of(h/λ)optand the maximum sensitivity Sfm λ maxincreases with the elastic constant cE66 of the piezoelectric substrate material. For the CFEC/[011]c poled PZN-7%PT single crystal sensor configuration, with the carbon fibers parallel to the x1 axis at λ = 24 μm, the maximum sensitivity Sfm maxcan reach as high as 1156 cm2/g, which is about three times that of a traditional SiO2/ST quartz structure gravimetric sensor. The better design selection is to have the carbon fibers parallel to the direction of propagation of Love wave in order to obtain the best sensitivity.     

Release of charges under external fields of PbLa（Zr,Sn,Ti）O3 ceramic

This paper investigates the pyroelectric of poled antiferroelectric (AFE) ceramic Pb 0.97 La 0.02 (Zr 0.69 Sn 0.196 Ti 0.114)O 3 and its remnant polarization dependence of hydrostatic pressure.The results show that the bound charges of poled sample can be released in short time by temperature field or pressure field.The released charge abruptly forms a large pulse current.The phenomena of released charge under external fields result in the ferroelectric-AFE phase transition induced by temperature or hydrostatic pressure.     

Structural stability and electronic properties of Au5Hn (n=1–10) clusters

A systematic study on the geometrical structures, electronic and magnetic properties of Au₅H _n (n=1–10) clusters has been performed by using the all-electron scalar relativistic density functional theory with generalized gradient approximation at the PW91 level. It is found that all Au₅H _n clusters prefer to keep the planar structures like pure Au₅ cluster, the Au₅ structures in Au₅H₄, Au₅H₅ and Au₅H₆ clusters are distorted obviously. The adsorption of a number of hydrogen atoms enhances the stability of Au₅ cluster and all Au₅H _n clusters are more stable than pure Au₅ cluster energetically. The odd-even alteration of magnetic moment is observed in Au₅H _n clusters and may be served as the material with tunable code capacity of “0” and “1” by adsorbing odd or even number of H atoms. It seems that the most favorable adsorption between Au₅ cluster and a number of hydrogen atoms takes place in the case that the odd number of hydrogen atoms is adsorbed onto Au₅ cluster and becomes Au₅H _n cluster with even number of valence electrons.     

The (ν1, ν4, ν2+ν3, ν3+ν5) Polyad of D3SiF around 1600 cm, Studied by High-Resolution FTIR Spectroscopy

The ν₁ (A₁, 1578.31 cm⁻¹)/ν₄(E, 1615.17 cm⁻¹) Si-D stretching dyad of D₃SiF has been studied by FTIR spectroscopy with a resolution of 2.4×10⁻³ cm⁻¹. Only weak interactions of Coriolis (ΔK=±1, Δ?=±1) and α resonance (ΔK=±2, Δ?=?1) type between ν₁ and ν₄, and of ? (2,−4) type within ν₄, were revealed. However, the v₁=1 and v₄=1 levels were found to be severely perturbed by the v₃=v₅=1 (E, 1590.37 cm⁻¹) and v₂=v₃=1 (A₁, 1604.25 cm⁻¹) states. These perturbations are observable only near level crossings involving strong Coriolis and α interactions. The energy structure within these perturbers is severely complicated by strong Coriolis and α resonances and by ? (2, 2), ? (2,−1), and ? (2,−4) interactions as already revealed by the ν₂(A₁, 710.16 cm⁻¹) and ν₅ (E, 701.72 cm⁻¹) fundamentals. Interactions of the perturbing states with the ν₁/ν₄ dyad are particularly evident in local crossings. In total, 12 transitions belonging to the dark states and 68 perturbation-allowed transitions within the ν₁/ν₄ dyad have been detected among the more than 5000 transitions that have been assigned for the ν₁/ν₄ dyad, with J_max and K_max of 50 and 30, respectively. Altogether about 85% of the assigned transitions were fitted with a standard deviation of 0.221×10⁻³ cm⁻¹, leading to 61 parameters of the interacting polyad.     

Luminescence of LiTb(PO3)4:Sm3+ and energy transfer from Tb3+ to Sm3+ under vacuum ultraviolet–ultraviolet excitation

The photoluminescence (PL) of LiTb(PO₃)₄, LiGd_0.97Sm_0.03(PO₃)₄, and LiTb_0.97Sm_0.03(PO₃)₄ under vacuum ultraviolet (VUV)/ultraviolet (UV) excitation were studied. We observed the VUV–UV sensitization of Sm³⁺ emission (561 nm, 601 nm, 649 nm, and 710 nm) by Tb³⁺ in LiTb(PO₃)₄:Sm³⁺, which leads to the yellow light emission (486 nm, 546 nm, 561 nm, 587 nm, 601 nm, 621 nm, 649 nm, and 710 nm) of LiTb(PO₃)₄:Sm³⁺ phosphor under UV and VUV excitation. The emission is a result of partial energy transfer from Tb³⁺ to Sm³⁺, which is discussed in detail in terms of the excitation and emission spectra and decay curves.     

Acousto-optic Q-switched laser performances of Er3+:Yb3+:LuAl3（BO3）4 crystal at 1.5-1.6 μm

Diode-pumped acousto-optic Q-switched pulse laser at 1.5-1.6 μm is obtained in an Er3+:Yb3+:LuAl3 (BO3)4 crystal. Single-pulse laser operation with slope efficiency of 14% and threshold of approximately 100 mW is realized at an average absorbed pump power of 314 mW and repetition frequency of 20 kHz. Output pulse energy is 67 μJ. The effects of pulse repetition frequency, absorbed pump power, and duty cycle on the wavelength and pulse profile of the Q-switched Er3+:Yb3+:LuAl3(BO3)4 laser are also investigated.     

The first high-resolution infrared study of diazirinone, N2CO: Analysis of the Fermi-coupled ν1 and 2ν5 bands

The first validated detection of the elusive diazirinone molecule (N₂CO) in the gas phase was performed using high-resolution infrared spectra recorded in the 1810–2100 cm⁻¹ region. The ν₁ and 2ν₅ bands were identified at 2043.8 and 1863.3 cm⁻¹ close to the ab initio prediction [X.Q. Zeng, H. Beckers, H. Willner, J.F. Stanton, Angew. Chem. Int. Ed. 50 (2011) 1720–1723]. For these two bands, the individual lines exhibit a (2:1) intensity alternation, confirming a three membered ring structure (C_2V symmetry) for N₂CO. The major output of the ν₁ and 2ν₅ bands analysis is the first experimental determination of the ground-state rotational constants of cyclic N₂CO. The observed intensity pattern of the ν₁ and 2ν₅ bands is in agreement with the existence of a strong Fermi resonance coupling the 1¹ and 5² energy levels.     

La7（1-x）P3O18:xDy3+的白光发光性能

使用高温固相法制备了La_7（1-x）P₃O₁₈:xDy³⁺发光材料,在347nm激发下,其发射峰分别为480、578、664nm,分别对应离子Dy³⁺能级内的⁴F_9/2→⁶H_15/2、⁶H_13/2和⁶H_11/2跃迁。随着Dy³⁺浓度的增加,黄光和蓝光的强度的比值逐渐减小,当Dy³⁺浓度为2mol%时,发光强度最大,计算出的色坐标处于白光区域内（0.33,0.33）,该材料的发光颜色随Dy³⁺浓度的变化而在白光区域内改变,因此,该材料可作为紫外激发的白色发光材料。     

Structural and physical properties of undoped and nickel-doped BaFe2-xNixAs2（x = 0,0.04） single crystals

<正>Single crystals of undoped and nickel-doped BaFe_(2-x)Ni_xAs_2(x=0,0.04) have been grown by FeAs self-flux method.The maximum dimension of the crystal is as large as ~ 1 cm along the ab plane.The crystalline topography of a cleaved crystal surface is examined by scanning electron microscope(SEM).By x-ray powder diffraction(XRD) experiments using pure silicon as an internal standard,precise unit cell parameters(tetragonal at room temperature) are determined:a = 3.9606(4) A(1 A=0.1 nm),c = 13.015(2) A for BaFe_(1.96)Ni_(0.04)As_2 and a = 3.9590(5) A,c = 13.024(1) A for BaFe_2As_2.DC magnetization and transport measurements are performed to check superconducting transition(T_c=15 K for x=0.04) and other subtle anomalies.For BaFe_(0.96)Ni_(0.04)As_2 crystal,the resistance curve at normal state shows two distinct anomalies associated with spin and structure transitions,and its magnetization data above ~ 91 K exhibit a linear temperature dependence due to spin density wave(SDW) instability.     

Improving luminescent property of SrIn2 O4 :Eu3+ by co-doped A+ （A = Li, Na, K） or Sm3+

A series of SrIn2 O4 :Eu3+ phosphors are synthesized by a high temperature solid-state method, and their luminescent properties are investigated. They can be excited by 395-nm radiation, and produce red emission (619 nm); however, they have a low absorption of near-ultraviolet light with the wavelength of 400nm-405 nm. When co-doped with A+ (A=Li, Na, K), the emission intensity of SrIn2O4 :Eu3+ is significantly enhanced, but its emission and excitation spectral profile is unchanged. With co-doping Sm3+ , not only is the emission intensity of SrIn2 O4 :Eu3+ enhanced, but also the absorption is broadened and strengthened in the range of 400 nm-405nm. The effect of Sm3+ -doped content on the emission intensity of SrIn2O4 :Eu3+ , Sm3+ is investigated, and the optimal Sm3+ content is 0.02 mol.