EPR of a new defect in natural quartz: Possibly O-2

The EPR of a new defect in natural quartz has been measured with principal g-values 2.318(1), 1.972(1) and 1.959(1). ²⁹Si hyperfine interaction is found with one neighbouring Si site. The direction of the axis corresponding to the largest principal value of the g-tensor, is close to the direction joining two oxygen neighbours of a silicon vacancy. This and other evidence suggests that the center may be O^-₂.     

Generation of O-2 molecular ions in electron-irradiated KBr and KI crystals

It is shown that during electron irradiation of KBr and KI crystals at 80 K a vibronic structure develops in the emission spectrum characteristic of O^-₂ molecular ions. The origin of these ions is explained in terms of the processes following the radiolysis of OH^- impurity ions. Total disappearance (thermal quenching) of the vibronic structure T#62;170 K for KBr and T#62;110 K for KI is attributed to the reaction between mobile X^-₂ (V_k) centres and O^-₂ molecular ions resulting in the formation of optically inactive O₂ molecules.     

The three reorientation processes of O-2 centres in unstressed alkali halide crystals

Measurements of the reorientation of O^-₂ centres in RbI and RbBr at low temperatures together with earlier measurements in different alkali halides suggest the following sequence of relaxation mechanisms in an unstressed srystal: Below about 3°K a one phonon tunneling process, then an activated tunneling process through the first librational state, and above 10°K a classical jumping process over the potential well.     

The characteristics of doubly and triply charged ions C2^2＋, C2^2- and C2^3＋

Based on group theory and atomic and molecular reaction statics, this paper derives the possible electronic states of C^{2+}_2, C^{2-}_2 and C^{3+}_2, and their reasonable dissociation limits and determines their ground electronic states C^{2+}_2(X^3Π_u), C^{2-}_2(X^1Σ^+_g) and C^{3+}_2(X^4Σ^-_u) using quantum mechanical calculations at the level of QCISD/6-311G^*. All the potential energy curves of their ground states have both a minimum and a maximum, which are the so-called "energy trapped" molecules. This sort of potential maximum is chiefly due to Coulomb repulsion. We propose the perturbation effect of ionic charges, which is used to explain why the orbital degeneracy of diatomic ions may be removed. The characteristics of potential curves for diatomic ions are briefly described.     

Pseudo potential calculations for Na+2, K+2, Rb+2 and Cs+2

A Hellmann type pseudopotential, is used to calculate the six lowest Σ potential energy curves of Na⁺₂, K⁺₂, Rb⁺₂ and Cs⁺₂ molecular ions.     

Analytical Potential Energy Function for Doubly Charged Ions O2+2, Be2+2 and He2+2

A new analytical potential function is proposed in our preceding paper as which can be used to describe the potential curves for doubly charged diatomic ions with both potential minimum and maximum where ρ=R-Rmin, if R=Rmin, ρ=0, if R=Rmax, ρ=Rmax-Rmin. The parameters a1～a4 are obtained by a least-squares fit based on the ab initio calculations, the values of parameters Rmin and Rmax are fixed from the same calculations. The application of this function is quite flexibly, for it can be also used to describe the potential curves without any potential minimum and maximum, i.e., no stationary point, where ρ=R. The present paper is to examine the proposed potential function form further by describing potential curves of O2+2, Be2+2 and He2+2. The calculations using the theoretical method CID with basis set 6-311++G* have showed the Rmin() and Rmax() to be 1.045 and 1.60, 2.141 and 3.50, and 0.736 and 1.05 for the ground state X1Σ+g of O2+2, Be2+2 and He2+2, respectively, which are in good agreement with reference data. The analytical potential function for the ground state of these doubly charged diatomic ions have been successfully derived for the first time     

The N+2 laser

Results of an experimental investigation of a gas-discharge pulse laser on the transition of the N⁺₂ molecule (λ = 4278 Å) are given. The time and spectral characteristics of the output radiation have been measured.     

MO study of counter anions of TMTSF: Electronic structure of NO−3, BF−4, ClO−4 and FSO−3

The electronic structure and geometrical structure of NO^-₃, BF^-₄, ClO^-₄ and FSO^-₃ anions are studied by means of the ab initio molecular orbital method. According to the results obtained, the central atoms of these anions are all positively charged and the surrounding atoms negatively charged. The bonding nature of ClO^-₄ and FSO^-₃ is similar to that of XF^-₆ (X = P, As and Sb) previously studied, and has a coordination-like character. However, BF^-₄ and NO^-₃ show a covalent-like character. The ion radii of these anions are determined from the total density contour maps obtained by the calculation.     

Luminescence as an indication of distortion in A3+2 B4+2 O7 type pyrochlores

The Eu³⁺ luminescent emission spectra of rare-earth titanate, titanate-stannate, stannate, hafnate and zirconate pyrochlores, A³⁺₂B⁴⁺₂O₇, indicated that a linear relationship existed between the splitting of the ⁵D₀ → ⁷F₁ magnetic-dipole transition and the size of the cation present. Small A³⁺ cations and larger B⁴⁺ cations both produced a lattice with a lesser degree of deviation from O_h symmetry.     

含硼盐卤体系中碳酸根和碳酸氢根分析方法改进

利用甘露醇法测定硼、双指示剂法测定总碱度,同时借鉴血清中HCO-₃的检测方法,建立了一种分光光度-滴定分析联用方法,用于准确测定含硼盐卤体系中硼及CO2-₃和HCO-₃的准确含量。以酚红为显色剂,考察了测定波长、显色剂用量、显色反应温度、pH等测试条件的影响,并从浓度与吸光度的线性关系,检出限及加标回收率等方面进行了系统研究,结果表明：在显色剂用量为1 mL,控制pH 8.4,室温下进行显色反应;在波长558 nm处,CO2-₃在0~10 mmol·L-1内吸光度与浓度有良好线性关系,线性相关系数R2=0.999 8,检出限为2.53×10-3 mmol·L-1。样品加标回收率范围在97.75%~101.76%间,相对误差在-1.67%~-1.95%。该方法简便易行,精密度好,准确度高,优化了共存硼体系中CO2-₃和HCO-₃含量的测定方法,为含硼盐卤体系中体系碳酸根和碳酸氢根含量的准确测定提供了一种新的方法,对于盐湖卤水的基础研究和实际应用提供了新的思路和实验方法。     

Mo study on charge distributions in octahedral PF−6, AsF−6 and SbF−6 anions

The charge distributions in octahedral PF^?₆, AsF^?₆, and SbF^?₆ anions are studied by means of the ab initio molecular orbital method. We find that the central P, As, and Sb atoms are all positively charged in these anions, while F atoms negatively charged, the order of the positive charge being Sb > P > As.     

Cross sections for slow ion production and charge transfer in H+3(D+3)−H2(D2) collisions

Slow ion production cross sections for collisions of H⁺₃ and D⁺₃ ions with H₂ and D₂ have been measured at collision energies between 100 eV and 500 eV. The values vary from 2 × 10^-17 cm² to 6 × 10^-17 cm². The smaller cross sections for D₃ projectiles may be explained as an internal energy effect.     

超短强激光脉冲与H2＋相互作用研究：经典与量子计算的比较

用经典动力学和量子力学方法分别研究了Ｈ２＋在超短强激光场中的电离、离解和残存行为，得到了相似的结果：即在超短强激光脉冲作用下，Ｈ２＋的电离占优，但有限的量子计算低估了Ｈ２＋的离解几率；而经典处理则没有显示Ｈ２＋在超强场中的稳定化。另外，经典计算表明当核间距Ｒ伸展到一定范围时，Ｈ２＋的电离率最大。这符合量子计算中发现的电荷谐振增强电离（ＣＲＥＩ）现象。     

Ionization by H+2. Molecular effect

The molecular effect in the ionization of inner shell electrons of aluminum atoms by energetic H⁺₂ molecules has been calculated. We distinguish between the molecular effect in Al and Al₂O₃. We conclude that in the case of Al the protons of the cluster have a definite orientation but in the case of Al₂O₃ the orientation is at random.     

Kr2F1 and Kr12 radiative lifetime measurements

Atomic krypton was excited in presence of SF₆ by an intense electron beam. The radiation emitted by the Kr₂F¹(²B₂→ A₁) transition was studied at 430 nm using time resolved spectroscopic techniques. The radiative lifetimes of Kr₂F¹ and of Kr¹₂ were found to be 200 ns and 270 ns respectively.     

HfO2/SiO2薄膜的激光预处理作用研究

对电子束蒸发方式镀制的HfO2/SiO2反射膜采用大口径激光进行辐照,采用激光量热计测量了激光辐射前后的弱吸收值。实验发现HfO2/SiO2反射膜在分别采用1 064 nm和532 nm的激光辐照前后薄膜吸收分别从5.4%和1.7%降低到1.4和1.2%。采用聚焦离子束技术分析了激光辐照后薄膜的损伤形态并探究了损伤原因,发现：薄膜在激光辐照下存在节瘤的地方容易出现薄膜损伤,具体表现为熔融、部分喷发、完全脱落3种形态,节瘤缺陷种子来源的差异是导致其损伤机理也存在着巨大差异的主要原因。同时这些节瘤缺陷种子来源也影响着激光预处理作用效果,激光预处理技术对于祛除位于基底上种子形成的节瘤是有效的,原因是激光辐射过后该节瘤进行了预喷发而不会对后续激光产生影响;而激光预处理技术对位于膜层中间的可能是镀膜过程中材料飞溅引起的缺陷是无效的,需要通过飞秒激光手段对该类节瘤进行祛除。     

Luminescence of Ba0.85MgAl10O16.94：Eu^2＋0.09 with different fluxes

BaMgAl10O17:Eu^2 , known as BAM, is a very important blue-emitting phosphor used in plasma display panels (PDP) and three band fluorescent lamps. In this paper, the Ba0.s5MgAl10O16.94:Eu^2 0.09 phosphors with different fluxes (BaF2, MgF2, AIF3, BaCl2, MgCl2, AICl3, H3BO3) were prepared by high temperature solid-state reaction method and the influence of different fluxes on the luminescence of Ba0.85MgAl10O16.94:Eu^2 0.09 phosphor was studied under 254nm excitation and vacuum ultraviolet (VUV) excitation. It was found that fluorides have better flux effects than chlorides and H3BO3. The mechanism of particle growth in the presence of flux in the process of phosphor preparation is discussed in detail. Particle size distribution and the crystal structure of the phosphors are also analysed.     

DYNAMICS of H+2 in TWO-COLOR ULTRASHORT LASER PULSE

Numerical simulations of ionization and dissociation processes of hydrogen molecular ion H₂⁺ interacting with two-color intense ( 10¹⁴W/cm²-10¹⁵W/cm²) ultrashort (the duration ≈ 22fs) laser pulse are made. The result shows that the ionization and dissociation processes are strongly dependent upon the relative phase between the two color fields. It means that, in the case of ultrashort pulse, the phase coherence control of ionization and dissociation processes can be realized.     

HfO_2/SiO_2薄膜的激光预处理作用研究北大核心CSCD

激光预处理是提高激光薄膜抗激光损伤阈值的重要手段。对电子束蒸发方式镀制的HfO2/SiO2反射膜采用大口径激光进行了辐照,并采用激光量热计测量了激光辐射前后的弱吸收值。采用聚焦离子束(FIB)技术分析了激光辐照后薄膜的损伤形态并探究了损伤原因,首次采用扫描电镜拍摄到了节瘤部分喷发时的形貌图,并对其进行了FIB分析,为进一步了解节瘤的损伤过程提供了依据。实验发现,激光辐照过后的激光薄膜弱吸收明显降低,激光预处理有效减少了引起薄膜吸收的缺陷,存在明显的清洗效应;在本实验采用的HfO2/SiO2反射膜中,激光预处理技术对于祛除位于基底上种子形成的节瘤是有效的,原因是激光辐射过后该节瘤进行了预喷发并不会对后续激光产生影响;而激光预处理技术对位于膜层中间的可能是镀膜过程中材料飞溅引起的缺陷是无效的,需要通过其他手段对该类节瘤进行祛除。     

BF+2注入加固硅栅PMOSFET的研究

系统地研究了BF⁺₂注入硅栅P-channel metal-oxide-semiconductor field-effect transistor(PMOSFET)阈值电压漂移与γ辐照总剂量之间的关系,深入地探讨了BF⁺₂注入抗γ辐射加固的机理.结果表明,BF⁺₂注入对硅栅P-channel metal-oxide-semiconductor(PMOS)在γ辐照下引起的阈值电