Variation of potential energy surface height and bound state depth induced by laser phase along the reaction path in atom-molecule reactions: Application to Li + CH<Subscript>4</Subscript> → LiH + CH<Subscript>3</Subscript>

Laser atom-molecule reaction interaction through polarizability and dipole moment contribution leads to potential energy surface barrier reshaping and bound states along the reaction path. The polarizability is maximum in the transition state. We will show here by using gauge representation (electric field gauge) for wave length λ = 20.6 μm, intensity I = 1 × 10¹² W/cm², I = 5 × 10¹² W/cm², I = 1 × 10¹³ W/cm², I = 3 × 10¹³ W/cm², that we can create laser induced potential energy surface barrier reshaping in the transition state region (–1–0.5 a. u.). We illustrate such effects for the LiH + CH₃ ? Li + CH₄ reaction with a barrier using ab-initio methods for calculating the reaction path, polarizability and dipole moment contribution of the atom-molecule reaction.     

PRECISE MEASUREMENT OF DENSITY-DEPENDENT SHIFT BY WAVELENGTH MODULATION REFLECTION SPECTROSCOPY

The density dependence of the line shift of the cesium D₂ line is studied with sub-Doppler selective reflection spectroscopy. By use of wavelength modulation and sixth-harmonics detection we observed the coefficient of the pressure-induced shift of the 6S_1/2(F=4)→6P_3/2(F'=3) hyperfine transition of the cesium D₂ line Δδ/ρ=-0.9(5)×10^-8cm³. In the limit ρ=0 a frequency shift about -3MHz remains, which may be attributed to long-range atom－surface interactions. The experimental results can be used in measurements of the local field-induced frequency shift at high atomic densities with sufficient accuracy.     

锗、硅、锑化铟和砷化镓的热膨涨——用X射线衍射法测量

本工作是用X射线衍射法测量锗、硅和合金InSb及GaAs在不同温度的点阵常数,观察它们的热膨涨,并求得它们的膨涨系数。     

用低能弱γ源测量电子对的近阈产生截面

用2.7μCi的⁶⁰Co弱γ源和NaI(Tl)与Ge(Li)双探测器符合测量方法,测量了Al,Zn,Sn,Pb四种样品的电子对产生绝对截面。测量结果与前人用很强γ源得到的结果相符合,并验证了在近阈条件下,对产生截面满足Jaeger关系式:σ_pair=(Z²+aZ⁴)σ₀,求得对⁶⁰Co源γ光子,α=(1.51±0.23)×10^-4,σ_{0关键词：}     

Numerical Simulations of femtosecond-laser-induced dynamic alignment of molecules in the high-frequency off-resonance regime

The motion equation for ? between the molecular axis and laser polarization direction in a high-frequency off-resonance femtosecond laser field is deduced while simultaneously examining the effects of a permanent dipole moment and field-induced polarizability and hyperpolarizability to molecular rotation. Femtosecond-laser-induced dynamic alignment of CO, N₂, and Br₂ molecules are investigated by numerically solving the obtained rotation equation for the angle ?. The effects of the molecular permanent dipole moment and the field-induced polarizability and hyperpolarizability on the degree of alignment are presented at different intensities. Our computational results show that the dynamic alignment of molecules is primarily determined by field-induced polarizability and the second hyperpolarizability for the laser intensity range from 5 × 10¹⁴ to 5 × 10¹⁶ W/cm². The contributions of higher order correction terms to molecular alignment can usually be neglected. The polarizability-field interaction makes the angular distributions of a molecule have a maximum along the polarization axis and a minimum perpendicular to it. The role of the second hyperpolarizability keeps the molecular counts maximum along the laser polarization direction but minimum at an angle of 45° between the molecular axis and the polarization direction. There is also a second maximum of molecular counts perpendicular to the polarization axis. For CO, N₂, and Br₂ molecules, the dependences of laser-induced dynamic alignment on laser intensity exhibit completely different characteristics.     

类铍离子低激发态等电子系列的能量、精细结构和超精细结构

采用多组态相互作用方法及Rayleigh-Ritz 变分方法，并考虑相对论修正和质量极化效应，获得了类铍离子等电子系列（Z=4-10）低激发态1s²2p2p ¹D^e和1s²2p3p ³P^e的相对论能量。同时还计算了精细结构和超精细结构。计算结果与其他理论和实验符合的很好。     

CALCULATION OF THE TRANSITION ENERGIES OF THE Ne-LIKE IONS WITH THE CORRECTION OF CORE POLARIZATION

The transition energies between n=3 and n=2 of the Ne-like ion Ge²²⁺, Se²⁴⁺, Zr³⁰⁺, Rh³⁵⁺, Ag³⁷⁺, Sb⁴¹⁺, Xe⁴⁴⁺, La⁴⁷⁺, Nd⁵⁰⁺ and Eu⁵³⁺ are calculated by adding polarization in the core. The systematic errors in multi-configuration Dirac-Fock calculation are greatly reduced and a good agreement is obtained between the theory and the experiment. This study shows that introducing the polarization of core orbitals is a good method to calculate the atomic structure, and there is a close relation between polarizability and nucleus charge.     

Radiative corrections for pion polarizability experiments

We use the semi-analytical program RCFORGV to evaluate radiative corrections to onephoton radiative emission in the high-energy scattering of pions in the Coulomb field of a nucleus with atomic numberZ. It is shown that radiative corrections can simulate a pion polarizability effect. The average effect is α _π ^rc =?β _π ^rc =(0.20±0.05)×^?43 cm³, for pion energies 40–600 GeV. We also study the range of applicability of the equivalent photon approximation in describing onephoton radiative emission.     

One-electron spectrum of Lu2+: Relativistic energies,transition probabilities and dipole polarizability

Calculations are reported of relativistic model-potential ionization energies and transition probabilities in the one-electron spectrum of doubly ionized lutetium. The approach employed includes both valence-core electron exchange and correlation. The influence of polarization of the core by the valence electron on ionization energies and transition probabilities has been studied. Strong cancellation effects, similar to those found previously for the Yb(II) spectrum, have been found for higher transitions of the principal series. Energies are predicted for some states that have not yet been determined experimentally. Computed oscillator strengths for the principal series are employed to obtain a tentative value for the static dipole polarizability of the doubly-ionized lutetium ground state … 4f¹⁴6s²S_{$\text{1}\text{2}$}.     

基态S和D原子的低能弹性碰撞及SD(X2Π)自由基的准确相互作用势与分子常数

使用Gaussian03程序包提供的CCSD（T）理论及Duning等的相关一致基cc-pVnZ和aug-cc-pVnZ （n=2, 3, 4, 5）, 对SD（X²Π）自由基的平衡核间距、谐振频率及相互作用势进行了计算, 并拟合出了相应的光谱常数. 在CCSD（T）/aug-cc-pV5Z理论水平下, 光谱常数D₀, D_e, R 关键词： 弹性碰撞 总截面 光谱常数 分子常数     

Doppelresonanzuntersuchungen zum Stark-Effekt des 4s 4p 3 P 1-Terms im Ca I-Spektrum

The influence of an electric field on the Zeeman-splitting of the 4s 4p ³P₁-level was investigated using the double resonance method. From the r.f.-resonance signals the tensor polarizability of the 4s 4p ³ P ₁-level was deduced to be α_ten(³ P ₁)=3.2(8) kHz/(kV/cm)². This value is used for an estimate of the oscillator strength of the infrared transition between the multiplets 4s 4p ³ P and 4s3d ³ D. Taking into account measured oscillator strengths of electric dipole transitions from the³ P ₁-level to other low lying levels one obtainsf(4s 4p ³ P→4s 3d ³ D)=0.09.     

QED and hyperfine splitting in the 2s1/2−2p3/2 X-ray transition in lithium-like Bi80+

The measurement of the Bi⁸⁰⁺ 2s_1/2−2p_3/2 transition energy is discussed. The measurement resolved the hyperfine splitting of the (1s²2s) F=4,5 ground configuration and allowed a determination of the Lamb shift contributions with a precision of about 9 × 10^-4 providing the most accurate test of QED in a high-Z ion to date. This revised version was published online in July 2006 with corrections to the Cover Date.     

掺铒铋酸盐玻璃的光谱性质研究

研究了掺铒铋酸盐玻璃的吸收和荧光光谱性质,应用Judd-Ofelt理论计算了玻璃的三个强度参量Ω_t=(t=2,4,6),分别为Ω₂=3.71×10^-20cm²,Ω₄=1.86×10^-20cm²,Ω₆=1.28×10^-20cm²,计算了Er³⁺离子的自发跃迁几率、荧光分支比等光谱参量.经荧光谱测试发现掺Er³⁺铋酸盐玻璃的荧光半高宽可达70nm.应用McCumber理论计算1.53μm处的受激发射截面可达9×10^-21cm².对Er³⁺离子在不同基质玻璃中光谱特性的比较发现,Er³⁺在铋酸盐玻璃中具有相对较高的受激发射截面和宽的荧光半高宽.     

Radiative de-excitation of the 1s22s3 p 3P0 level in beryllium-like ions: A competition between an E2 and a two-electron one-photon E1 transition

I have performed a complete Multi-Configuration Dirac-Fock calculation of the radiative de-excitation of the 1s²2s3p³P₀ level in beryllium-like ions. Initial and final wave functions are fully optimized, and include valence and core polarization correlation (Coulomb and Magnetic). Non-orthogonality between initial and final state spin-orbitals is exactly accounted for. I show that the main mode of de-excitation of the 1s²2s3p³P₀ level at high Z is an E2 transition to the 1s²2s2p³P₂ and that a two-electron one-photon E1 transition to the 1s²2p^{2 3}P₁ plays an important role at low Z. The latter transition appears to be the difference of two large matrix elements which cancel almost exactly and thus has a very complicated Z dependence, which is studied in the present paper. This revised version was published online in August 2006 with corrections to the Cover Date.     

α-Al2O3单晶中Fe3+离子的电子顺磁共振

本文对α-Al₂O₃单晶体中Fe³⁺离子在室温下,X波段进行了电子顺磁共振研究,发现Fe³⁺离子实际上占据四种磁性不等价晶位。在同一氧离子层间的两种晶位上的Fe³⁺离子具有相同的自旋哈密顿参量,而不同氧离子层间的晶位上的Fe³⁺离子具有不同的自旋哈密顿参量,两种自旋哈密顿参量为:(1)g_‖=2.001,g_⊥=2.003,D=1679 关键词：     

Kβ X-ray emission from He-like ions

Relativistic calculations on the energies and electric dipole rates of K_β X-rays from 1s3p(¹P₁,³P₁)-1s² (¹S₀) transitions for He-like ions in the range Z=14–54 are carried out using multi-configuration Dirac–Fock (MCDF) wave functions in the active space interaction approach. The contributions from Breit interaction and quantum electrodynamics have also been included in the calculation. An attempt has been made to find a scaling expression for Breit energy in terms of Zα .The scaled Breit energies are in good agreement with the earlier accurate relativistic results and this ensures the reliability of our scaling procedure. The behavior of MCDF wavefunctions for a given J in the non-relativistic limit has also been studied. The calculated K_β X-ray energies and rates agree well with other available experimental and theoretical values.     

Doppelresonanzuntersuchung des Einflusses eines elektrischen Feldes auf die Zeeman-Aufspaltung des 5s 5p 3P1-Terms im SrI-Spektrum

Under the simultaneous action of external electric and magnetic fields the 5s 5p ³ P ₁-level of the even Sr-isotopes splits into three non-equidistant Zeeman-sublevels. In an atomic beam experiment the spacings between the sublevels were investigated by the double resonance method at a magnetic field strength of ca. 22 Oe and at electric field strengths up to ca. 17 kV/cm. From the r.f.-resonance signals the tensor polarizability of the 5s 5p ³ P ₁-level was deduced to be α_ten(³ P ₁)=6.1(8) kHz/(kV/cm)². This value may be used to get an estimate of the oscillator strength of the infrared transitions between the multiplets 5s 5p ³P and 5s 4d ³ D. Taking into account oscillator strengths of electric dipole transitions to other low lying levels one obtainsf(³ P→³ D)≈0.09.     

ABO3型晶体中氧的电子自发极化

计算O^-2在晶体场中出现的Jahn-Teller效应,得到具有电矩的2p_π3s3d₀杂化原子轨道。BO₆八面体共价性质决定了ABO₃晶体的各种极化相。理论给出P_s比值、钛位移大小和热力学参数ξ′,ζ′均接近于实验结果。统一解释了钛酸钡的三个相转变。相变条件给出七种晶体中氧的屏蔽常数平均值与Slater的值一致。     

The kinetics of donor-acceptor pair transitions with strong phonon coupling in GaP

Donor-acceptor pair luminescence in GaP was studied by time-resolved spectroscopy, by measuring and analysing the integral band decay over many decades of intensity and time and by measuring and analysing the temperature dependence of the luminescence intensity. We report here the results obtained with some or all of these techniques for pairs involving deep as well as shallow centres. Those with a deep centre are: S_P-Si_P and Si_Ga-Si_P, in which the acceptor is the deep centre, and O_P-C_P and O_P-Zn_Ga, in which the donor is the deep centre. These pairs all have a broad, phonon-dominated luminescence band. The pairs involving shallow centres include Si_Ga-C_P, S_P-C_P and Te_P-C_P. Due to the different way of momentum conservation in these pairs, those involving a donor on a Ga-site have strong phonon co-operation and weak zero-phonon (ZP) transitions, whereas those with a donor on a P-site have strong ZP transitions.With time-resolved spectroscopy, well-resolved structure, due to a ZP pair band and its phonon replicas, is obtained for nearly all pairs. A comparison is made with the structure obtained by measuring in the stationary state at very low excitation densities. Some trends in the strength of phonon co-operation are noted. In the case of Si_Ga-C_P pairs, sharp replicas of ZP pair lines with a momentum-conserving phonon are also resolved.Using the integral band decay technique and results from time-resolved spectroscopy we have determined the transition probabilities for the total luminescence band as well as for the ZP band for nearly all pairs mentioned. The influence of incomplete saturation of the pairs during excitation with a focussed beam of an argon-ion laser is discussed and approximately corrected for. Extrapolated to zero pair separation, the total transition probability ranges from ∽ 10⁵s^-1 for Si_Ga-C_P pairs to ∽ 15 × 10⁵s^-1 for O_P-C_P and O_P-Zn_Ga pairs. The ZP probability ranges from ∽ 4 × 10³s^-1 for Si_Ga-C_P and Si_Ga-Si_P pairs to ∽ 4 × 10⁵s^-1 for S_P-C_P pairs. The transition probability for pairs in GaP is discussed in relation to the site occupied by the donor and the depth of the centres involved. The relatively high dope concentrations used in some cases, ∽ 1 to 2 × 10¹⁸cm^-3, are discussed briefly in relation to “concentration quenching”.The temperature dependence of the luminescence intensity of S_P-Si_P pairs is satisfactorily analysed with a simple linear model. The same model is applied to similar literature data on the S_P-C_P pair luminescence. Using in addition data on the average pair transition probability, trapping rate constants for hole capture by the Si_P and C_P acceptors were calculated to be ∽ 10^-9 cm³s^-1. Evidence is presented that the trapping rate constant for holes by the Zn_Ga-O_P complex is about 2 × 10^-9 cm³s^-1.     

TheE1 transitions in kaonic atoms

The electric dipole transition rates in kaonic atoms are calculated by using distorted relativistic wave functions. The kaon-nucleus strong interaction which is responsible for the distortion of atomic states is considered to be proportional to the nuclear density and the effective isospin-averaged kaon-nucleon scattering length. Six atoms have been studied for which the last observed X-rays correspond to 3d-2p, 4f-3d, 5g-4f, 6h-5g, 7i-6h and 8j-7i transitions. It is found that the electric dipole transition rate is enhanced by an amount (0.3–7.6)×10¹³s^?1