Isomorphous substitution in bimetallic oxide clusters

The geometric and electronic structure of bimetallic oxide clusters is studied as a function of their composition with gas phase vibrational spectroscopy. Infrared multiple photon dissociation spectra of titanium-vanadium oxide cluster anions are measured in the 500 to 1200 wave number range and assigned on the basis of harmonic frequencies calculated using density functional theory. Singly substituted (V(2)O(5))(n-1)(VTiO(5))(-) (n=2-4) cluster anions are shown to form polyhedral caged structures similar to those predicted for their isoelectronic counterparts, the neutral (V(2)O(5))(n) clusters. Upon systematic exchange of V by Ti atoms in V(4-n)Ti(n)O(-)(10) (n=1-4), the structure does not change. The stress induced by the isomorphous substitution results in an increased number of unpaired electrons (n-1) for the Ti-rich systems, leading to a quartet ground state for Ti(4)O(-)(10).     

用密度泛函方法研究质子化苯基丙酮-水团簇

应用密度泛函B3LYP/631+G(d,p)计算方法,对质子化苯基丙酮水团簇这个弱相互作用体系进行了全自由度能量梯度优化,得到该系列团簇的稳定结构.结果表明,H+C8H8OH2O团簇的形成过程为一无能垒的反应过程,在质子与C8H8O分子中O原子的距离为1.015时达到平衡几何.对H+C8H8O(H2O)n(n=1,2,3)团簇,质子位于C8H8O分子和水分子之间,且随着团簇尺寸的增加,质子与C8H8O分子中O原子之间的距离也增加;C8H8OH+H2O可以视为溶剂壳.而对H+C8H8O(H2O)n(n=4,5,6,7,8)团簇,质子位于两个水分子之间,形成H5O2+结构,即C8H8OH5O2+为该系列团簇的中心结构,新增加的水分子以从不同方向进攻这个中心的方式形成更大尺寸的团簇.     

The proton inventory technique in a dual mechanistic system: the spontaneous hydrolysis of ethyl formate †

Ethyl formate undergoes spontaneous hydrolysis through two parallel mechanistic pathways: water catalysis and specific hydrogen-ion catalysis. The proton inventory of the water reaction at 37.0 ^°C was determined from the overall conversion curves, in H₂O/D₂O mixtures of deuterium atom fraction n, resulting in k ₁(n)=(2.1±0.1)×10^?5 s^?1 (1?n+0.42 n) (1?n+0.83 n)², in agreement with the results of six other cases of carboxylic acid derivatives. This result contributes to the validation of the accuracy of the proton inventory technique.     

Adiabatic decoupling sidebands

An analytical solution is given for amplitudes and phases of adiabatic decoupling sidebands as a function of spin inversion time tau. Since all the adiabatic decoupling phases theta(t, tau) refocus at two periods (2T) of the decoupling pulse, the sidebands are located at n/2T rather than at n/T as observed in other decoupling schemes. The real (R(n)(tau)) and imaginary (I(n)(tau)) amplitudes of the sidebands have symmetry R(n)(tau) = R(-n)(tau) and I(n)(tau) = -I(-n)(tau), forming a mirror image between the counterparts of the sidebands. When frequency sweep changes direction all I(n)(tau) are inverted while all R(n)(tau) remain unchanged, leading to pure absorption sidebands with two accumulations as demonstrated by Kupce and Freeman, and to an exchange of sidebands between counterparts. The sum of the real parts for sidebands n = 1 and 2 is almost a constant near on-resonance decoupling, and it increases substantially for large decoupling offsets. The phase defocusing can be minimized for all decoupling offsets by inserting an initial decoupling period with T(ini) = T/2, eliminating all sidebands located at n/2T (n = +/-1, +/-3, +/-5, ...).     

Evidence of two dimensionality in quasi-one-dimensional cobalt oxides

The quasi-one-dimensional (Q1D) cobalt oxides A(N + 2)Co(n + 1)O(3n + 3) (A = Ca, Sr, and Ba, n = 1 - infinity) were investigated by muon-spin spectroscopy under applied pressures of up to 1.1 GPa. The relationship between the onset Néel temperature T(on)(N) and the interchain distance (d(ic)), which increases monotonically with n, is well fitted by the formula T(N)/T(N,0) = (1 - d(ic)/d(ic,o)(beta), here for T(on)(N) approximately 100 K for Ca(3)Co(2)O(6) (n = 1) and approximately 15 for BaCoCoO(3) (n = infinity at ambient P. The T(on)(N) - d(ic) curve also predicts a large dependence of Y(N) for the compounds with n > or = 5, i.e., in the vicinity of , while the compounds show only a very small effect. Indeed, our high-pressure mu(+) results show that of BaCoO(3) is enhanced by with a slope of 2.2 K(Gpa), whereas no detectable changes by P for both Ca(3)Co(2)O(6) and Sr(4)Co(3)O(9) (n = 2). This clearly confirms the role of the 2D-antiferromagnetic interaction on T(on)(N) in the Q1D cobalt oxides.     

Stimulated desorption of cations from pristine and acidic low-temperature water ice surfaces

Electron-impact ionization of low-temperature water ice leads to H+, H+2, and H+(H2O)(n=1-8) desorption. The 22 eV H+ desorption threshold is correlated with localized 2-hole 1-electron and 2-hole final states which Coulomb explode, while the 22 eV H+2 threshold is due to H2O+ unimolecular dissociation. The 70 eV primary cluster ion threshold is consistent with holes in the 2a(1) level and secondary ionization channels. All cation yields are sensitive to local structural changes and probe surface acidity. The cluster size distribution indicates hole-hole screening distances of 1-2 nm.     

Intermolecular coulomb decay at weakly coupled heterogeneous interfaces

Surface ejection of H(+)(H(2)O)(n=1-8) from low energy electron irradiated water clusters adsorbed on graphite and graphite with overlayers of Ar, Kr or Xe results from intermolecular Coulomb decay (ICD) at the mixed interface. Inner valence holes in water (2a(1)(-1)), Ar (3s(-1)), Kr (4s(-1)), and Xe (5s(-1)) correlate with the cluster appearance thresholds and initiate ICD. Proton transfer occurs during or immediately after ICD and the resultant Coulomb explosion leads to H(+)(H(2)O)(n=1-8) desorption with kinetic energies that vary with initiating state, final state, and interatomic or molecular distances.     

甲醇/水混合团簇的多光子电离质谱研究

利用多光子电离技术结合飞行时间质谱仪对甲醇/水混合团簇进行了研究.在脉冲激光波长为355 nm条件下观测到团簇离子.主要的电离产物为质子化的(CH3OH)n(H2O)H+(n=l-13)混合团簇离子与(CH3OH)nH+团簇离子,经分析(CH3OH)1o(H2O) H+和(CH3OH)3H+为幻数结构.甲醇水混合团簇电离后团簇离子发生内部质子化转移反应是形成质子化团簇离子的主要原因.不同尺寸团簇离子信号强度随电离激光光强变化的光强指数曲线显示,团簇均发生四光子电离过程.     

Effects of a parallel magnetic field on the metal-insulator transition in a dilute two-dimensional electron system

The temperature dependence of conductivity sigma(T) of a two-dimensional electron system in silicon has been studied in parallel magnetic fields B. At B = 0, the system displays a metal-insulator transition at a critical electron density n(c)(0), and dsigma/dT>0 in the metallic phase. At low fields ( B < or approximately equal to 2 T), n(c) increases as n(c)(B)-n(c)(0) proportional, variant Bbeta ( beta approximately 1), and the zero-temperature conductivity scales as sigma(n(s),B,T = 0)/sigma(n(s),0,0) = f(B(beta)/delta(n)), where delta(n) = [n(s)-n(c)(0)]/n(c)(0) and n(s) is electron density, as expected for a quantum phase transition. The metallic phase persists in fields of up to 18 T, consistent with the saturation of n(c) at high fields.     

Study of deuteron-proton charge exchange reaction at small transfer momentum

The charge exchange reaction at 1 GeV projectile proton energy is studied in the multiple-scattering expansion technique. This reaction is considered in a special kinematics, when the momentum transfer from the beam proton to the fast neutron is close to zero. The differential cross-section and a set of polarization observables are calculated. It was shown that the contribution of the final-state interaction between two protons is very significant.Received: 29 April 2004, Published online: 5 October 2004PACS: 21.45. + v Few-body systems - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy 10 GeV) - 25.45.Kk Charge-exchange reactions     

Air- and N(2)-Broadening Parameters of Water Vapor: 604 to 2271 cm(-1)

High-resolution measurements of air- and N(2)-broadened widths and pressure-induced frequency shifts of water vapor were obtained covering the spectral region between 604 and 2271 cm(-1). Over 1300 vibration-rotation transitions were measured including the (000)-(000), (010)-(010), (010)-(000), (020)-(010), and (100)-(010) vibrational bands of H(2)(16)O. Also included were measurements of H(2)(18)O and H(2)(17)O from normal water vapor samples and H(2)(18)O + N(2) observations with oxygen-18-enriched gas samples. Collision-narrowing effects were observed in a few lines involving high J and low K(a) transitions with the lowest measured linewidth coefficient equal to 0.0057(4) cm(-1)/atm (air-broadening) for the completely overlapping transitions, 17 0 17 <-- 18 1 18 and 17 1 17 <-- 18 0 18, at 1235.204 cm(-1). The majority of the linewidth values were derived from the measurements using a Voigt line profile. A few lines with air- or N(2)-broadened half-width values of about 0.012 cm(-1) or less were found to exhibit collision-narrowing effects and were also analyzed with a profile proposed by Galatry. The results are compared to values given in previous studies. Copyright 2000 Academic Press.     

Tuning the continuum ground state energy of NO2- 2 by water molecules

Electron scattering on NO-2, NO-2 x (H2O), and NO-2 x (H2O)(2) was performed in two storage rings. We confirm the presence of earlier reported NO2-2 dianion resonances and show that they remain when water is attached. Importantly, hydration tunes the energy: each water molecule lowers the ground state energy by 0.8 +/- 0.3 eV relative to the monoanion. NO2-2 is observed to decay by two-electron emission, possibly in combination with fragmentation. NO(2-)2 x (H2O) mainly decays into NO-2 + H2O + e(-).     

n+1维双sine-Gordon模型的Coleman相变

本文计算了n+1维双sinc-Gordon模型的高斯有效势,在高斯有效势近似下,证明:n≥3的模型是平凡的,n<3的模型存在一个Coleman相交点,临界耦合参数为β_cr=(2ⁿ⁺²π^(n+1)/2(α_1R+α_2R/4)^(3-n)/2)/(Γ(1/2(3-n))(α_1R+α_2R/16)). 关键词：     

含O3MoS3单元的配合物[Mox（CO）y（O,S—C6H4—1,2）3FezLm[^n—（x=1,2或3,y=0,3

用红外光谱研究标题配合物的结构,得到了很有意义的结果。     

Effect of shear on phase-ordering dynamics with order-parameter-dependent mobility: the large-n limit

The effect of shear on the ordering kinetics of a conserved order-parameter system with O(n) symmetry and order-parameter-dependent mobility Gamma(straight phi-->) approximately (1-straight phi-->(2)/n)(alpha) is studied analytically within the large-n limit. In the late stage, the structure factor becomes anisotropic and exhibits multiscaling behavior with characteristic length scales (t(2alpha+5)/ln t)(1/2(alpha+2)) in the flow direction and (t/ln t)(1/2(alpha+2)) in directions perpendicular to the flow. As in the alpha=0 case, the structure factor in the shear-flow plane has two parallel ridges.     

Investigation on damage of BSA molecules under irradiation of low frequency ultrasound in the presence of FeIII-tartrate complexes

The interaction between bovine serum albumin (BSA) and Fe(III)-tartrate complexes ([Fe(III)(tar)(H(2)O)(3)](-) and [Fe(III)(tar)(2)](5-)) as well as the damage of BSA in the presence of Fe(III)-tartrate complexes under ultrasonic irradiation was studied by UV-vis and fluorescence spectra. In addition, the influences of ultrasonic irradiation time, Fe(III)-tartrate complex concentration, ionic strength and solution acidity (pH value) were also examined on the damage of BSA. The results showed that the fluorescence quenching of BSA caused by the Fe(III)-tartrate complexes belonged to the static quenching. The BSA and Fe(III)-tartrate complexes interacted with each other mainly through weak interaction and coordinate actions. The corresponding binding association constants (K) and the binding site numbers (n) were calculated. The results were as follows: K(1)=1.67x10(3)Lmol(-1) and n(1)=0.9699 for [Fe(III)(tar)(H(2)O)(3)](-), K(2)=1.54x10(3)Lmol(-1) and n(2)=0.8754 for [Fe(III)(tar)(2)](5-). Otherwise, under ultrasonic irradiation the BSA molecules were obviously damaged by the Fe(III)-tartrate complexes. The damage degree rose up with the increase of ultrasonic irradiation time, Fe(III)-tartrate complex concentration, pH value and ionic strength. And that, [Fe(III)(tar)(H(2)O)(3)](-) exhibited higher sonocatalytic activity in a way than [Fe(III)(tar)(2)](5-).     

Autocorrelation exponent of conserved spin systems in the scaling regime following a critical quench

We study the autocorrelation function of a conserved spin system following a quench at the critical temperature. Defining the correlation length L(t) approximately t(1/z), we find that for times t' and t satisfying L(t')infinity limit, we show that lambda(')(c)=d+2 and phi=z/2. We give a heuristic argument suggesting that this result is, in fact, valid for any dimension d and spin vector dimension n. We present numerical simulations for the conserved Ising model in d=1 and d=2, which are fully consistent with the present theory.     

Stabilized Tunable Diode Laser Measurements of the P(2) Line in the (13)CO Fundamental Band Broadened by Helium at Temperatures between 11.5 and 298.6 K

We determined accurate He-broadening parameters and collisional cross sections for the P(2) line in the fundamental band of CO at room temperature and at intermediate temperatures down to 11.5 K. We also determined a precise value for the temperature dependence of the line-broadening parameter on (T)(-n) with n equal to 0.548+/-0.010. Our results validate the microwave results for the J=1 to J=2 rotational transitions measured over the same range of temperatures which were reported previously by Beaky et al. (1996, J. Chem. Phys. 105, 3994-4004). Copyright 2001 Academic Press.     

蓝绿粉(掺Eu2+硼磷酸锶)的发光特性随其组份及温度的变化

本文报导了利用激光感生荧光技术研究蓝绿粉材料2(Sr1-xEux)0·(1-n)P2O5·nB2O3,在不同掺杂浓度x、结合基浓度n的情况下,其发光寿命及发光光谱的变化情况。研究范围在0.001≤x≤0.100,0.01≤n≤0.90。另外,还研究了蓝绿粉在不同温度(室温～400℃)时的发光特性。为配制最佳组份的蓝绿粉提供了实验依据。     

Two New Zn(II)/Cu(II) Compounds: Photoluminescent and Photocatalytic Properties,and Protective Activity on Parkinson Disease

Journal of Fluorescence - Two coordination polymers, that is [Zn(pdc)(im)(H2O)]n (1) and [Cu(pdc)(im)2]n·n(H2pdc) (2) (H2pdc?=?terephthalic acid, im?=?imidazole), were...