81Br NQR Study of [NH3(CH2) n NH3]CdBr4 (n = 4 and 5) and [NH3(CH2) n NH3]ZnBr4 (n = 5 and 6)

⁸¹Br NQR frequencies and differential scanning calorimetry (DSC) were measured as a function of temperature. [NH₃(CH₂)₄ NH₃]CdBr₄ (1) and [NH₃(CH₂)₅NH₃]CdBr₄ (2) showed a doublet and quartet ⁸¹Br NQR spectrum, respectively. [NH₃(CH₂)₅NH₃]ZnBr₄ (3) and [NH₃(CH₂)₆NH₃]ZnBr₄ (4) exhibited a four-line ⁸¹Br NQR spectrum. From the NQR results, it is inferred that (1) and (2) consist of infinite two-dimensional sheets of corner-sharing CdBr₆ octahedra, whereas (3) and (4) have isolated [ZnBr₄]²⁻ tetrahedra. All of the crystals except (1) showed at least one structural phase transition above 380 K.     

First-principles study of the difference in permittivity between Ba(Mg1 / 3Ta2 / 3)O3 and Ba(Mg1 / 3Nb2 / 3)O3

This paper discusses the difference in permittivity at infrared frequencies between Ba(Mg_1/3Ta_2/3)O₃ (BMT) and Ba(Mg_1/3Nb_2/3)O₃ (BMN) based on a first-principles calculation. The permittivity, far-infrared and Raman spectra are successfully computed. Analysis of these results shows that the smaller amplitude of O in the low frequency mode E_u² (BMT), which is caused by the larger polarizability of Ta⁵⁺, is the origin of the smaller permittivity of BMT.     

Polarizabilities of rubidium (9-10)S 1/2 and 8D 3/2, 5/2 states

Polarizabilities of several rubidium states were determined by measuring stark shifts of transitions using an electro-optically modulated laser beam to excite an atomic beam. The voltage required for atoms excited by the laser beam in an electric field to be simultaneously in resonance as atoms excited by a frequency sideband of the laser in a field free region was measured. The scalar α and tensor α ₂ polarizabilities were found to be: α (9 S _1/2 ) = 103.77±0.09, α (10 S _1/2 ) = 272.54±0.16, α (8 D _3/2 ) = 230.68±0.25 and α ₂ (8 D _3/2 ) = 26.55±0.10, α (8 D _5/2 ) = 222.68±0.14 and α ₂ (8 D _5/2 ) = 51.91±0.10 MHz/(kV/cm)². The results are 100 times more accurate than previous measurements and are within 1% of those found theoretically using a Coulomb approximation calculation. Received 7 September 2000 and Received in final form 6 December 2000     

Experimental determination of the potential energy curves of the I(3/2u) and I(3/2g) states of Kr+ 2

The I(3/2u) and I(3/2g) states of Kr⁺ ₂ have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy following (2 + 1′) resonance-enhanced multiphoton excitation via the 0⁺ _g Rydberg state located below the Kr?([4p]⁵5p[1/2]₀) + Kr(¹S₀) dissociation limit of Kr₂. From the positions of a large number of vibrational bands in the spectra of the ⁸⁴Kr₂ and ⁸⁴Kr-⁸⁶Kr isotopomers, the adiabatic ionization potentials (IP(I(3/2u)) = 112672.4 ± 0.8cm^?1, IP(I(3/2g)) = 111 395.0 ± 1.4cm^?1), the dissociation energies (D ⁺ ₀(I(3/2u)) = 368.8 ± 2.0cm^?1, D ⁺ ₀(I(3/2g)) = 1646.2 ± 2.3cm^?1) and vibrational constants for both ionic states have been determined. Potential energy curves have been extracted which perfectly reproduce all experimental observations and are accurate over a wide range of energies and internuclear distances. The equilibrium internuclear distances (R ⁺ _e(I(3/2u)) = 4.11 ± 0.04 Å, R ⁺ _e(I(3/2g)) = 3.35 ± 0.10 Å) have been derived by comparing the intensity distribution in the PFI-ZEKE photoelectron spectra to calculated Franck-Condon factors. The dissociation energy of the I(3/2g) state and the equilibrium internuclear distance of the I(3/2u) state differ markedly from previously reported values.     

Dissociation energies of the I(3/2g) and I(1/2g) states of Ar+ 2

Rotationally resolved pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of ⁴⁰Ar₂ and ³⁶Ar₂ have been recorded between 124650cm^?1 and 127 150cm^?1 following resonant two-photon excitation via the 0⁺ _u (v¹= 0) Rydberg state located below the Ar (¹S₀) + Ar?((3p)⁵4s′ [1/2]₁) dissociation limit. Four overlapping vibrational progressions were observed and attributed to transitions to the I(1/2u) u⁺ = 35–50, I(3/2g) u⁺ = 0–10, I(1/2g) v⁺ = 0–6 and I(3/2u) v⁺ = 0–2 vibronic states of Ar⁺ ₂. The vibrational quantum numbers of the ionic states were derived from an analysis of the isotopic shifts, and the dissociation energies of the I(3/2g) (D⁺ ₀(⁴⁰Ar⁺ ₂:) = 1509.4 ± 1.2cm^?1) and the I(1/2g) (D⁺ ₀(⁴⁰Ar⁺ ₂) = 616.3 ± 1.2cm^?1) states were determined.     

The NMR study of the mixed compound (CH3NH3)2Cu(Cl0.1Br0.9)4

The mixed compound (CH₃NH₃)₂Cu(Cl_0.1Br_0.9)₄ which has random bonds of ferromagnetic and antiferromagnetic interactions has been investigated by the pulsed NMR of ¹H, ^63,65Cu and ^79,81Br. The temperature dependence of the line width of ¹H showed the existence of the magnetic phase transition at 15 K in the applied field of 4 kOe. The moments of Cu²⁺ have been shown to lie within the c-plane and have some randomness from the field dependence of the NMR spectrum and the spin-echo decay time of the copper and the bromine nuclei.     

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

Quasi-classical trajectory theory is used to study the reaction of O(³P) with H₂ (D₂) based on the ground ³A' potential energy surface (PES). The reaction cross section of the reaction O+H₂ → OH+H is in excellent agreement with the previous result. Vector correlations, product rotational alignment parameters 〈P₂ (j'·k)〉 and several polarized-dependent 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.     

Vibration Spectra and Structural Characteristics of Ba[(Zn1-x Mg x )1/3Nb2/3]O3 Solid Solutions

Abstract

The Ba[(Zn_1-x Mg _x )_1/3Nb_2/3]O₃ (BZMN, x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solution ceramics were synthesized by the conventional solid-state reaction method. Vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection [FTIR] spectroscopy) and X-ray diffraction (XRD) were employed to evaluate the correlation between crystal structures and vibration modes of these solid solutions as a function of Zn²⁺ ions replaced by Mg²⁺ ions. Spectroscopic and structural data show sensitivity to the sample structural evolution with Mg²⁺ concentration, and a 1:2 ordered structure appears for Mg-rich samples where x ≥ 0.6. The Ba[(Zn_0.4Mg_0.6)_1/3Nb_2/3]O₃ has a 1:2 ordered monoclinic unit cell, which is distorted by the antiphase tilting of the oxygen octahedra. The phonon modes were assigned, and a correlation of phonon vibrations with the microstructure was found. The position and width of the phonon modes were determined and correlated to the ionic radii, mass, and tolerance factors for the different atoms substituted in the B′-site.     

Quadrupole relaxation enhancement and polarisation transfer in DMSO solution of [Bi(NO3)3(H2O)3]*18-crown-6 in solid state

ABSTRACT

¹H spin-lattice relaxation studies have been performed for pure [Bi(NO₃)₃(H₂O)₃]*18-crown-6 in powder and its solution in dimethyl sulfoxide (DMSO). The experiments have been carried out in the frequency range of 10?kHz–30?MHz and the temperature range of 240–277?K; at 277?K the solution is already frozen. The ¹H relaxation of pure [Bi(NO₃)₃(H₂O)₃]*18-crown-6 has been interpreted in terms of three dynamical processes. Quadrupole Relaxation Enhancement effects have been observed in the frozen DMSO solution of [Bi(NO₃)₃(H₂O)₃]*18-crown-6. The specific mechanisms of the ¹H spin-lattice relaxation enhancement have been discussed distinguishing between effects caused by time independent (residual) and fluctuating ¹H-²⁰⁹Bi dipole-dipole interactions.     

Microwave spectrum of (CH3)3CCN-SO3

Eight rotational transitions of the complex (CH₃)₃CCN-SO₃ have been recorded using pulsed-nozzle Fourier transform microwave spectroscopy and a series of ab initio calculations has been performed. The complex is a symmetric top with free or nearly free internal rotation of the SO₃ and (CH₃)₃CCN subunits. The nitrogen-sulfur bond distance is determined to be 2.394(19) Å. Calculations at the MP2/aug-cc-pVTZ level/basis, which are in excellent agreement with the experimental results, give a binding energy of 11.0 kcal/mol relative to (CH₃)₃CCN and SO₃. Physical properties of the system, including N-S bond length, N-S-O angle, binding energy, and the degree of electron transfer (obtained from Townes and Dailey analysis of the ¹⁴N nuclear quadrupole coupling constant) are compared with those of similar complexes. The proton affinity of the base is a useful parameter for ordering complexes in the series.     

IR Spectra of Be(IO3)2.nH2O (n = 4, O) and of the Deuterated Analogue

Abstract

The compounds of beryllium - Be(IO₃)₂.4H₂O, its deuterated analogue and Be(IO₃)₂ were studied by IR-spectroscopy over the range of 200 to 4000 cm^?1.     

Preparation and ferroelectric properties of pyrochlore-free Pb(Ni1/3Nb2/3)O3-based solid solutions

Polycrystalline ceramics of the perovskite solid solution 0.5Pb(Ni_1/3Nb_2/3)O₃-(0.5-x)-Pb(Zn_1/3Nb_2/3)O₃–xPb(Zr_1/2Ti_1/2)O₃; x=0.0–0.5 (PNN–PZN–PZT) were synthesized by a modified columbite method. Highly dense ceramics lacking parasitic pyrochlore phases were prepared at a calcination temperature of 950 °C by using a double-crucible configuration, excess PbO (2 mol %), and a fast heating/cooling rate (20 °C/min). The ceramics were characterized by a variety of techniques including X-ray diffraction, ferroelectric hysteresis loop measurements, field-induced longitudinal strain measurements, and electron microscopy. It was observed that the remanent polarization exhibited a significant increase with increasing x. In addition, the squareness of the hysteresis loop increased quasi-linearly as the molar fraction of PZT increased. The maximum spontaneous polarization and remanent polarization for the x=0.5 composition were 31.9 μC/cm² and 25.2 μC/cm², respectively. Moreover, the data were analyzed to show the evolution of the micro-domain state as a function of the molar fraction of PZT. PACS 77.22.-d; 77.80.Bh; 77.84.Dy; 61.10.Nz; 77.80.Dj     

钙钛矿型晶体A(B1/31B2/32)O3中的有序-无序相变

本文利用原子集团变分方法,讨论了A⁺²(B_1/3⁺²B_2/3⁺⁵)O₃系统中有序-无序相变,指出在此系统中相互作用能参数对形成(B_2/3⁺²B_1/3⁺⁵)_1/2:B_1/2⁺⁵=1:1的混合型有序畴和B_{1/3关键词：}     

Ferroelectric properties of bilayer structured Pb(Zr0.52Ti0.48)O3/SrBi2Ta2O9 (PZT/SBT) thin films on Pt/TiO2/SiO2/Si substrates

Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films with large remanent polarization and SrBi₂Ta₂O₉ (SBT) thin films with excellent fatigue-resisting characteristic have been widely studied for non-volatile random access memories, respectively. To combine these two advantages_, bilayered Pb(Zr_0.52Ti_0.48)O₃/SrBi₂Ta₂O₉ (PZT/SBT) thin films were fabricated on Pt/TiO₂/SiO₂/Si substrates by chemical solution deposition method. X-ray diffraction patterns revealed that the diffraction peaks of PZT/SBT thin films were completely composed of PZT and SBT, and no other secondary phase was observed. The electrical properties of the bilayered structure PZT/SBT films have been investigated in comparison with pure PZT and SBT films. PZT/SBT bilayered thin films showed larger remanent polarization (2P_r) of 18.37 μC/cm² than pure SBT and less polarization fatigue up to 1 × 10⁹ switching cycles than pure PZT. These results indicated that this bilayered structure of PZT/SBT is a promising material combination for ferroelectric memory applications.     

Characterization of the VUV excitation spectrum of BaZr(BO3)2:Eu

The excitation spectra of M (M=Si⁴⁺, Ti⁴⁺) and Eu³⁺ co-doped BaZr(BO₃)₂, BaZrO₃:Eu and La₂Zr₂O₇:Eu in the vacuum ultraviolet (VUV) regions of 110-300 nm are investigated and the host-lattice absorption are characterized. The result indicated that BaZr(BO₃)₂:Eu³⁺ phosphor has a strong absorption under the VUV excitation, and in the host-lattice excitation, the strong band at 130-160 nm could be due to the BO₃ atomic groups; the band at 160-180 nm is related to the excitation of Ba-O; 180-200 nm corresponds to the charge transfer (CT) transition of Zr-O. The band at 200-235 nm due to the CT band of Eu³⁺-O²⁻ and a bond valence study explained the observed weak CT band of Eu³⁺-O²⁻ in the excitation spectra of BaZr(BO₃)₂:Eu³⁺. The emission results show that Si⁴⁺ can sensitize luminescence in the host of BaZr(BO₃)₂:Eu but Ti⁴⁺ has no improvement effect on luminescence.     

Er3+，Tm3+共掺的NaY(WO4)2晶体的光谱分析和上转换发光

在室温下，测量了Er:Tm:NaY(WO₄)₂晶体的吸收光谱、激发光谱、发射光谱以及上转换发光，并运用J-O理论对测量的结果进行了计算，得出了Er:Tm:NaY(WO₄)₂晶体的强度参数.报道了Tm，Er离子间特殊的能量传递和相关上转换，解释了离子间的能级跃迁过程.同时，对于Er增强Tm离子近红外发光的特性也作了充分研究. 关键词： 4)₂晶体')" href="#">Er:Tm:NaY(WO₄)₂晶体 吸收光谱 发射光谱 激发光谱 上转换     

Action of monoatomic cations on the structure and spectra of Mx(1)M1-x(2)UO2(NO3)3 crystals

The action of the monovalent M⁺ cations on the luminescent properties of the mixed M _x ⁽¹⁾ M _1-x ⁽²⁾ UO₂(NO₃)₃ crystals, where M is Na, K, Rb, Cs, or NH₄ , has been investigated. It has been established that the spectral positions of the bands of vibronic transitions depend linearly on the ratio between the concentrations of the M⁽¹⁰⁾ and M⁽²⁾ cations. It is shown that the crystals considered are composed of l[RbUO₂(NO₃)₃]n[CsUO₂(NO₃)₃] clusters, where l/n = x/(1 - x). The spectral regularities revealed are determined by the partial contributions of the M⁽¹⁾ and M⁽²⁾ cations to their combined, polarizing action on the uranyl complex and are explained by the ligand nature of its highest occupied molecular orbital.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 827–830, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Stark shifts and fine structure of the Li 3 D states

⁶Li 3²D _{3/2, 5/2} states were studied using a diode laser to first excite the 2P _3/2 state and a dye laser to populate the 3²D _{3/2, 5/2} states. The dye laser was modulated by an electro-optic modulator and intersected an atomic beam that passed through a field free region and subsequently through a uniform electric field. A value of 1084.24±0.20 MHz was found for the 3²D fine structure splitting. The scalar and tensor polarizabilities were determined to be α (3D _3/2 ) = - 3.753±0.015, α ₂ (3D _3/2 ) = 2.893±0.017, α (3D _5/2 ) = - 3.772±0.008 and α ₂ (3D _5/2 ) = 4.058±0.013 MHz/(kV/cm)². Received 26 September 2002 / Received in final form 22 January 2003 Published online 11 March 2003 RID="a" ID="a"e-mail: wlaser@yorku.ca     

Synthesis and photoluminescence properties of MZr2(PO4)3:Eu3+; Bi3+ (M=Na; K) phosphors

A series of new red phosphors, MZr₂(PO₄)₃:Eu³⁺; Bi³⁺ (M=Na; K), were synthesized using the solidstate reaction method, and their photoluminescence spectra were measured. The MZr₂(PO₄)₃:Eu³⁺; Bi³⁺ (M=Na; K) phosphors were efficiently excited by an ultraviolet (UV; 395 nm) source, and showed intense orange-red emission at 595 nm. Further investigation of the concentration-dependent emission spectra indicated that the MZr₂(PO₄)₃:Eu³⁺; Bi³⁺ (M=Na; K) phosphors exhibit the strongest luminescence intensity when y = 0.01 in NaZr_2(0:95−y)(PO₄)₃:Eu_0.10³⁺, Bi_2y ³⁺ and y = 0.09 in NaZr_2(0.95−y)(PO₄)₃:Eu_0.10³⁺, Bi_2y ³⁺, whereas the relative PL intensity decreases with increasing Bi³⁺ concentration due to concentration quenching. The addition of Bi³⁺ widens the excitation band of NaZr_2(0.95−y)(PO₄)₃:Eu_0.10³⁺, Bi_2y ³⁺ around 320 nm, which provides the useful idea of broadening the excitation band around 300–350 nm to fit the ultraviolet chip.     

钪原子的自电离里德伯能级3d4s(1D2)nf2 D3/2,3d4s(1D2)nf2 F5/2和3d4s(1D2)np2 D3/2<

在多通道量子亏损理论框架下,利用相对论多通道理论,分别在冻结实近似和考虑偶极极化下计算钪原子的J^π=(3/2)^-,(5/2)^-的三个收敛于 3d4s(¹D₂)的自电离里德伯系列的能级.对3d4s(¹D₂)np²D_3/2和3d4s(^{1 关键词： 相对论多通道理论 多通道量子亏损理论 电子-电子关联 自电离里德伯系列}