First-principles investigation of diffusion behaviours of H isotopes:From W(110) surface into bulk and in bulk W

<正>The diffusion behaviours of hydrogen（H）,deuterium（D）,and tritium（T） from W（110） surface into bulk and in bulk W are investigated using first-principles calculations combined with simplified models.The diffusion energy barrier is shown to be 1.87 eV from W（110） surface to the subsurface,along with a much reduced barrier of 0.06 eV for the reverse diffusion process.After H enters into the bulk,its diffusion energy barrier with quantum correction is 0.19 eV. In terms of the diffusion theory presented by Wert and Zener,the diffusion pre-exponential factor of H is calculated to be 1.57×10^-7 m²·s^-1,and it is quantitatively in agreement with the experimental value of 4.1×10^-7 m²·s^-1. Subsequently,according to mass dependence(（1/m）^1/2) of H isotope effect,the diffusion pre-exponential factors of D and T are estimated to be 1.11×10^-7 m²·s^-1 and 0.91×10^-7 m²·s^-1,respectively.     

Radiative lifetimes and tensor polarizabilities of 1s4f 1 F and 1s5f 1 F level of He I

He atoms have been excited by Ne⁺ ion impact and the depolarization of the fluorescence lines at 668 nm and 492 nm by magnetic and electric fields has been studied. The Ne⁺ ion energy could be chosen such that pure cascade level crossing signals were observed. From the widths of magnetic depolarization signals the radiative lifetimes τ(1s4f ¹ F)=74(2) ns and τ(1s5f ¹ F)=133(5) ns have been determined. By investigating the electric field splitting of the magnetic depolarization signals the tensor polarizabilities ¦α _ten(1s4f ¹ F)¦=0.58(1) kHz/(V/cm)² and ¦α _ten(1s5f ¹ F)¦=4.2(1) kHz/(V/cm)² have been deduced. From the latter value a mean frequencyv(1s5g?1s5f)=14.4 GHz of the transitions between the levels of the 1s5f configuration and those of the 1s5g configuration has been derived.α _ten(1s4f ¹ F) depends sensitively on the singlet-triplet mixing in the 1s4f configuration and thus a mixing coefficient could be deduced for this configuration.     

Untersuchungen zum Stark-Effekt metastabiler Terme im Ba I-Spektrum durch Nachweis von Hochfrequenzübergängen

By detection of r.f.-transitions between Zeeman-sublevels the Zeeman-splitting of the metastable 6s 5d-levels and of the 6s 6p³ P ₁-level of the even Ba-isotopes was investigated under the influence of an electric field in addition to a magnetic field. From the measurements the following tensor polarizabilities were deduced: α_ten(³D₃)=?29(5) kHz/(kV/cm)², α_ten(³ D ₂)=?13(3) kHz/(kV/cm)², α_ten(³D₁)=?10(2) kHz/(kV/cm)², α_ten(¹ D ₂)=?16(3) kHz/(kV/cm)². No effect due to electric fields up to 50 kV/cm was observed in the Zeeman-splitting of the 6s 6p ³ P ₁-level. Therefore the tensor polarizability of the 6s 6p³P₁-level must be much smaller than those of the 6s 5d-levels. The results will be discussed by considering the oscillator strengths both of the infrared transitions between the two multiplets 6s 5d ³ D and 6s 6p ³ P and of transitions to other low lying levels.     

BF+2注入多晶硅栅F迁移特性的分析与模拟

在深入分析BF⁺₂注入多晶硅栅F在多晶硅栅中迁移特性的基础上，建立了F在多晶硅栅中的迁移方程.采用有限差分法，模拟了BF⁺₂注入多晶硅栅F在多晶硅栅中的分布.模拟结果与二次离子质谱(SIMS)分析结果相符.给出了80keV，2×10¹⁵cm^-2 BF⁺₂注入多晶硅栅900℃，30min退火条件下F在多晶硅中的发射系数e=6×10关键词：     

Temperature dependence of IR band strength for polyethylene

IR spectra at 150° K and detailed temperature curves for 150–310° K for the 965, 985, 1175, 1890, and 2010 cm^–1 bands are reported. The background bears a direct relation to temperature, whereas the bands have a negative temperature coefficient of intensity. The weakening of the 944 cm^–1 band is irreversible.     

Study of 1-3 PZT fibre/epoxy composite force sensor

Lead zirconate titanate (PZT) fibres were prepared by a powder-based extrusion method. Pre-sintered PZT powder mixed with poly(acrylic acid) was spun in a spinnerette to produce fibres. The fibre of ∼400 μm diameter was used to fabricate 1-3 PZT fibre/epoxy composite discs with different volume fractions (ϕ) of PZT. Since the ceramic fibres are rather brittle, their elastic properties cannot be measured directly. In order to determine the properties of the ceramic fibres, effective properties of the fibres/epoxy 1-3 composite were measured. By using a modified series and parallel model, the properties of 1-3 composites can be calculated. Then, the elastic coefficient s_33,fibre^E, relative permittivity ε_33,fibre^T and piezoelectric strain coefficient d_33,fibre of the ceramic fibre could be found. Ring-shaped PZT fibre/epoxy materials composites with different ϕ were fabricated to be used as the sensing material in force sensor applications. The ring-shape composite with ϕ=0.5 was installed into a housing and the sensor was calibrated by different methods and its sensitivity was found to be 144 pC/N within the frequency range of 0.5–6.4 kHz which is much higher than that of a quartz force sensor with a similar structure. PACS 07.07.Df; 72.80.Tm; 77.84.Dy     

Semiclassical method for calculating the energetic values of helium, lithium and beryllium atoms

In previous papers we have presented a wave model for conservative bound systems resulted from the equivalency between the Schrödinger and wave equations. We proved that the normal curves of the characteristic surface of the wave equation, denoted by C curves, are solutions of the Hamilton-Jacobi equation, written for the same system, and correspond to the same constants of motion as those resulting from the Schrödinger equation. In this paper we present a method for computing the energetic values of conservative bound systems which is based on the properties of the C curves. The method is applied to the 1s ² state of helium, 1s ²2s and 1s ²2p states of lithium and 1s ²2s ² state of beryllium. Our theoretical values are compared with experimental data taken from well-known books. The relative error of our method is less than 5 x 10^?3.     

Transition wavelengths for helium atom in weakly coupled hot plasmas

We have investigated the effect of surrounding plasmas on several singly excited and doubly excited meta-stable bound states of helium atom using highly correlated basis functions for singly excited S, P, D states and CI-type basis functions for doubly excited meta-stable D states. Plasma effect is taken care of by using a screened Coulomb (Yukawa) potential obtained from the Debye model that admits a variety of plasma conditions, and such a model plays an important role in plasma spectroscopy. The wavelengths for transitions from the 1snp ¹P° (n=2,3)→1s²¹S^e, 1snp ³P° (n=2,3)→1s2s ³S^e, 2pnp ¹P^e (n=3,4)→1s2p ¹P°, 2pnp ³P^e (n=2,3)→1s2p ³P°, 2pnd ¹D° (n=3,4)→1s3d ¹D^e, 2pnd ³D° (n=3,4)→1s3d ³D^e, 2p3p ¹P^e→2pnd ¹D° (n=3,4), 2pnd ¹D°(n=3, 4)→2p4p ¹P^e, 2pnp ³P^e (n=2,3)→2p3d ³D°, and 2pnp ³P^e (n=2,3)→2p4d ³D° of helium atom in plasmas for various Debye lengths are reported.     

LiAr, LiKr and LiXe excimers: Photochemical formation of the - bands

We investigated the photochemical formation of lithium-rare-gas excimers in the 3 state through the reaction of Li₂(2(C)) and the ground-state rare-gas atom. Lithium-rare-gas vapor mixture was prepared in the heat-pipe oven. We populated the 2(C)state of the Li₂ molecule using the XeCl excimer laser wavelength at 308 nm or the PTP dye laser wavelength at about 335 nm. The 3-1 transitions were observed with peaks at 414, 420 and 435 nm for LiAr, LiKr and LiXe, respectively. We estimated thermally averaged rate constants for these photochemical reactions, which are cm³s^-1 for LiAr, cm ³ s^-1 for LiKr and cm³s^-1 for LiXe. Ab initio potential-energy curves and transition dipole moments for LiKr were calculated applying the SCF MRDCI method. Available data for the LiAr and LiKr excimers are presented, including potential-energy curves, electronic transition dipole moments, and spectroscopic constants. Possible photochemical formation of these molecules in the excited states is discussed. We performed the quantum-mechanical spectral simulations of the LiAr and LiKr 3-1 transitions, using ab initio potential-energy curves. Received: 2 October 1998 / Received in final form: 25 January 1999     

Theoretical study of the spectra of the oxygen isoelectron series

By applying perturbation theory to the reciprocal of the nuclear charge (1/Z), the spectra of a series of oxygen-like ions (having configurations of the 1s²2s²2pⁿ, 1s²2s2pⁿ⁺¹, 1s²2pⁿ⁺², n =4 type) are calculated. The results of the calculation are compared with existing experimental data. The difference between the theoretical and experimental energies of the terms is 0.1–1%.     

Isotope shifts and hyperfine structure of the 6s-7p transitions in the cesium isotopes 133, 135, and 137

The 6s-7p transitions in cesium at 459.3 nm (7² P _1/2) and 455.5 nm (7² P _3/2) have been investigated by saturation spectroscopy in vapor cells, using a laser spectrometer with 500 kHz bandwidth in the blue spectral range. Isotope shifts as well as hyperfine splittings were determined for the isotopes 133, 135 and 137.     

Thermo-Sensitive Ba0.64Sr0.36TiO3 Thin Film Capacitors for Dielectric Type Uncooled Infrared Sensors

Ba_0.64Sr_0.36TiO₃ (BST) thin films are prepared on Pt/Ti/SiO₂/Si₃N₄/SiO₂/Si substrates by a sol-gel method. Thermo-sensitive BST thin film capacitors with a Metal-Ferroelectrics-Metal (M-F(BST)-M) structure are fabricated as the active elements of dielectric type uncooled infrared sensors. XRD are employed to analyze the crystallographic structures of the films. AFM observations reveal a smooth and dense surface of the films with an average grain size of about 35 nm. Rapid temperature annealing (RTA) process is a very efficient way to improve crystallization quality. The preferable annealing temperature is 800°C for 1 min. The butterfly shaped C-V curves of the capacitors indicate the films have a ferroelectric nature. The dielectric constant and dielectric loss of the films at 100 kHz are 450 and 0.038, respectively. At 25°C, where the thermo-sensitive capacitors work, the temperature coefficient of dielectric constant (TCD) is about 5.9 %/°C. These results indicate that the capacitors with sol-gel derived BST thin films are promising to develop dielectric type uncooled infrared sensors.     

Polarimetric fibre laser sensors using Er-doped fibre

A polarimetric fibre laser sensor with narrow polarization mode beat frequency bandwidth is demonstrated using a polarization-maintaining Er-doped fibre. The slope coefficients of 124kHz°C^-1 cm^-1 and 137kHz m^-1 are obtained for temperature change and longitudinal strain measurements, respectively. A new configuration of polarimetric fibre laser sensor is also demonstrated using a conventional Er-doped fibre as a gain medium and a short length of polarization-maintaining fibre as a sensing part.     

Investigations on Afterglows of Neon Gas Discharges

We report on the experimental and numerical investigations on afterglows of neon gas discharges, which are performed at the Eindhoven University of Technology. The studied gas pressure range extends from 1 to 100 torr, the discharge current from 1 to 100 mA. The densities of the 1s-levels are measured with the help of the selective excitation spectroscopy (fluorescence technique). In this way a great number of decay curves of the 1s-densities have been measured in the afterglow of neon gas discharges. From these curves the diffusion coefficient of the metastable 1s-atoms, the coefficients of atomic collisional transfer between the 1s₅- and 1s₄-level, as well as the three body collision coefficient between metastable 1s₅-atoms and neon ground state atoms have been determined. Besides these experiments a numerical model of the neon afterglows has been developed. With this model the afterglow phenomena can be simulated and the influence of the particular processes on the whole afterglow can be studied conveniently. Comparison is made between the experimentally and numerically obtained decay curves. For the application of the numerical model a number of starting conditions, such as radial density profiles, gas temperature, (relative) densities of the 1s-levels, have been measured. Results of these measurements are presented. Also with the help of the selective excitation spectroscopy the coefficients of atomic collisional transfer between the 2p-levels have been measured in the afterglow. From these results, together with the measured (relative) intensities of the neon spectral lines in the afterglow the partial recombination coefficients for the 2p-levels were calculated.     

内壳层电子激发(电离)诱发的电子波函数的弛豫及其对辐射跃迁概率的影响

利用多组态Dirac_Fock(MCDF)理论方法，通过对Ar原子在基组态3p⁶和激发组态1s^-14s，2s^-14s，2p^-14s，3s^-14s，3p^-14s情况下电子波函数的计算，系统地研究了不同内壳层电子激发(或电离)引起的电子波函数的弛豫现象以及由此导致的k_α和k_β线的跃迁波长和概率的变化情况，并与以往的理论结果进行了比较. 关键词： MCDF方法 弛豫效应 电子波函数 跃迁概率     

HYLLERAASIAN WAVE FUNCT/ON OF 2s2 1S OF HELIUM

A variatioual calculation of the energy of the 2s^{2 1}S state of helium has been carried out with the use of a wave function of the Hylleraasian type. The wave function is ψ=e^-0.2278s{1-0.17079s-0.063155u-0.013869t² +0.010044u²+0.0064785s²} where s,t u are in units of 4 times the first Bohr radius of hydrogen. The energy is E(2s^{2 1}S)=-1.5412Rh. compared with the value -1.4400 Rh obtained by the method of self-consistent field.     

Stark interaction in then s n p z 3 P 1 levels of zinc and cadmium

The tensor polarizabilities of then s n p z ³ P ₁ levels of Zn and Cd were measured using optical double resonance. From the rf-resonance signals in parallel electric and magnetic fields, the following tensor polarizabilities were deduced: Zn,α _ten(4s4pz ³ P ₁)=1.83(8) kHz/(kV/cm)²; Cd,α _ten(5s5pz ³ P ₁)=1.77(8) kHz/(kV/cm)². Theoretical values were calculated using Coulomb approximation. The results were then compared with previous theoretical and experimental values and, in addition, with values for Hg. Theoretical results obtained by a modified Sternheimer method (E.J. Robinson: J. Opt. Soc. Am.59, 782 (1969)) are in better agreement with the experimental values than the results of the Coulomb approximation calculations.     

Influence of heating rate on the crystalline properties of 0.7BiFeO3-0.3PbTiO3 thin films prepared by sol-gel process

0.7BiFeO₃-0.3PbTiO₃ (BFPT7030) thin films were deposited on SiO₂/Si substrates by sol-gel process. The influence of heating rate on the crystalline properties of BFPT7030 thin films were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). XRD patterns of the films showed that a pure perovskite phase exists in BFPT7030 films annealed by rapid thermal annealing (RTA) technique. SEM and AFM observations demonstrated that the BFPT7030 films annealed by RTA at 700 °C for 90 s with the heating rate of 1 °C s⁻¹ could show a dense, crack-free surface morphology, and the films’ grains grow better than those of the films annealed by RTA at the same temperature with other heating rates. XPS results of the films indicated that the ratio of Fe³⁺:Fe²⁺ is about 21:10 and 9:5 for the films annealed by RTA at 700 °C for 90 s with the heating rate of 1 and 20 °C s⁻¹, respectively. That means the higher the heating rate, the higher the concentration of Fe²⁺ in the BFPT7030 thin films.     

Recent hyperfine structure investigations in the configurations 4f 136s 2, 4f 136s6p,and 4f 125d6s 2 of Tm I

By use of optical hyperfine structure investigations in the Tm I spectrum theA- values of 20 levels of the configurations 4f ¹³ 6s 6p and 4f ¹² 5d 6s ² and theA-value of 4f ¹³ 6s ^{2 2} F _5/2 were determined very accurately. These data and tenA-factors from former experiments are used for theoretical calculations. 30A-factors have been interpolated from intermediate coupling wave functions using 9 effective mono-electronic parameters. The r.m.s. deviation between experimental and theoreticalA- values amounts to 0.5 10^?3 cm^?1 and represents 3/100 of the average value of the measuredA-factors.     

Hyperfine structure induced isotopic effects in krypton resonance ionization mass spectrometry

A time-of-flight mass spectrometer combined with a pulsed laser system has been used for determination of krypton isotope ratios of air samples containing 10⁶-10⁷ krypton atoms. A three-color, doubly resonant ionization scheme employing a 116.48 nm transition from the ground into the first 4s²4p⁵(²P°_1/2)5s J = 1 excitation level has been applied. The magnitude of a hyperfine splitting of this level has been estimated for ⁸¹Kr, ⁸³Kr and ⁸⁵Kr isotopes. Hyperfine structure induced isotopic effects have been investigated under different saturation conditions and found to be negligible when the first and the second transitions are strongly saturated.