Two-electron Excitation and Ionization in an Intense Laser Field

Abstract

We present a simple model for two-electron excitation and ionization of an atom in the presence of an intense laser field. We show, in particular, how the Coulomb interaction, via configuration interaction, prevents the excitation and ionization from being collective in all but the most intense fields. By collective we mean that each electron has the same spatial wavefunction: this implies that the electron pair may be described by a restricted time-dependent Hartree-Fock wavefunction. The configuration interaction prevents collective behaviour not only through the process of auto-ionization but also through the mixing of doubly excited independent electron states into the ground state. We are able to give criteria for establishing true collective excitation and ionization of our model two-electron system in an intense field.     

Relaxation Rates and Collision Integrals for Bose-Einstein Condensates

Near equilibrium, the rate of relaxation to equilibrium and the transport properties of excitations (bogolons) in a dilute Bose-Einstein condensate (BEC) are determined by three collision integrals, , , and . All three collision integrals conserve momentum and energy during bogolon collisions, but only conserves bogolon number. Previous works have considered the contribution of only two collision integrals, and . In this work, we show that the third collision integral makes a significant contribution to the bogolon number relaxation rate and needs to be retained when computing relaxation properties of the BEC. We provide values of relaxation rates in a form that can be applied to a variety of dilute Bose-Einstein condensates.     

激光陀螺数字式稳频方法的研究

提出了一套激光陀螺数字式稳频方案，在理论分析的基础上，设计并制作出数字式稳频硬件电路，同时编写了相应的稳频控制程序。实验结果表明：激光陀螺数字式稳频方法是可行的，且优于传统的模拟式稳频。     

Tunneling Rates of Single Electrons on Liquid Helium in an Extracting Field

We calculated the tunneling rates of single electrons from the quasi-stationary states on both liquid ⁴He and ³He in an extracting electric field. The rates were obtained from the widths of the resonance lineshapes of the asymptotic amplitude of the wave function for the electron. The calculations were carried out in the limit of strong tunneling which leads to tunneling rates of the order of 1 GHz, and is of recent interest in a proposed quantum-computer system using the electronic states of electrons on helium as qubits. We find that the resonances can, in general, be described by Fano lineshapes. Our results, in addition to presenting quantitative information involving the read-out operations of qubits, clarify that when tunneling is weak the resonances are sharp and more accurately Lorentzian and that the observed Fano lineshapes result from strong tunneling leading to fat resonances and hence asymmetry.     

激光测量回转机械振动的新方法

为了测量恒定转速上叠加的随机波动转速引起的振动,分析了回转机械转轴瞬时转速的表达关系,采用激光多普勒测量转轴瞬时转速的方法,测出了恒定转速上叠加的随机波动转速引起的振动.提出了一种信号处理方法,有效地克服了激光多普勒信号信噪比小、信号有时出现丢失的现象.对某电机升降速阶段的振动进行测试,振动是由于偏心引起的,电机的最大转速为4000 r/min.结果表明,此方法能够测试出恒定的转速上叠加的随机波动转速引起的振动.     

三角法激光测量系统的误差分析及消除方法

从理论和应用两方面分析了三角法激光测量系统的误差,得出：定点标定和插值可以消除光学放大率随测量点位置变化的影响;双光路方案或标准点校准方法可以消除光线路径随环境温度,湿度变化而引入的误差;提高激光束质量和采用峰值求光斑中心的方法,可以消除激光束强度分布,物体表面粗糙度,CCD传感器,信号处理电路等引入的误差。     

A Laboratory Method for Studying the Kinetics of Bleach-Fixing in Colour Processes

A laboratory method for studying Ihe kinetics of bleach-fixing in colour processes is outlined. Under the experimental conditions employed the kinetics of the bleach-fixing reaction can be interpreted in terms of two possible model. In the first, the rale of bleach-fixing exhibits a first order dependence on the available silver concentration, while in the second the reaction rate is governed by the diffusion rate of the reactants into the emulsion layer.     

一种无衍射激光图像亚像素边缘检测方法

为进一步提高无衍射激光图像的定中精度,提出了一种亮环亚像素级边缘点检测方法.首先,采用局域亮度最大方法,提取亮环像素级屋脊边缘点;然后,利用线性插值算法对每一像素级边缘点进行亚像素处理进而获得亚像素边缘点;最后,用最小二乘方法,将亚像素边缘点拟合定中.分别对距离光源40 m、50 m、60 m处,各连续拍摄的50幅图像(图像分辨率为640×480,光靶分辨率为0.057 2 mm/pixel)进行了处理,各位置处的亚像素级边缘点x方向定中标准差分别为0.021 4 nm、0.037 2 mm和0.042 3mm,y方向定中标准差分别为0.022 8 mm、0.035 1 mm和0.043 7 mm,明显优于像素级边缘点,实验结果表明,该方法切实可行.     

Use of Femtosecond Laser Technique for Studying Physically Small Cracks

Since small crack propagation behavior is strongly affected by microstructure, very small artificial notches with a length in the submillimeter range are needed for a systematic study of microcrack behavior. Laser processing technique with ultrashort pulses is a micromachining tool which will not cause any serious mechanical damage in metallic materials. Small artificial starter notches were manufactured in medium carbon steels with this technique and some fatigue tests were carried out. Laser affected zones could be observed at the notch boundary but cracks were initiated from the notch tips and propagated steadily. The crack paths were very tortuous like natural small cracks. The experimental results showed that the femtosecond laser processing technique is useful to introduce a small notch and allows systematic investigation of microcrack behavior.     

激光跟踪仪现场评定装置

介绍了一种用于激光跟踪仪现场快速评定装置,采用激光干涉仪作为标准器,能够生成任意标准长度,符合美国ASME B89.4.19的评价方法,同时还具有动态参数校准和角度标定功能,实现了激光跟踪仪在工业现场的快速评定.     

A Method of Measuring High Rates of Development

A simple apparatus has been constructed which enables plots of density against development time to be obtained for photographic materials that develop to completion in less than one second. The sheet of photographic material, uniformly pre-exposed. is rotated on a turntable at a known speed and developer is applied to it from a fixed position, forming a ring of developing emulsion. After developer has been applied for almost one revolution a photograph is taken of the moving sample together with a calibrated step wedge. Densities and development times are calculated from the resulting photograph.     

Drug Diffusion: A Field Gradient Electron Paramagnetic Resonance Study

Abstract

In order to gain information on the bioavailability of dermotherapeutics, field gradient electron paramagnetic resonance (FG EPR) spectroscopy was used. The characterisation of diffusion processes and distribution functions of different spin labeled molecules (Tempol, spin-labeled Lidocaine) within the ointment bases or skin is obtained by computer reconstruction of the spectra considering the diffusion concentration profiles derived from the model and comparison with the experimental FG EPR spectra.

Results on the diffusion in some ingredients of ointment bases, emulsion gels and skin showed, that this method furnishes reliable data on molecular transport in these systems. The translational diffusion coefficients are larger for hydrophilic media than for hydrophobic ones, where a good correlation with the dynamic viscosity was found.     

Drug Diffusion: A Field Gradient Electron Paramagnetic Resonance Study

In order to gain information on the bioavailability of dermotherapeutics, field gradient electron paramagnetic resonance (FG EPR) spectroscopy was used. The characterisation of diffusion processes and distribution functions of different spin labeled molecules (Tempol, spin-labeled Lidocaine) within the ointment bases or skin is obtained by computer reconstruction of the spectra considering the diffusion concentration profiles derived from the model and comparison with the experimental FG EPR spectra.

Results on the diffusion in some ingredients of ointment bases, emulsion gels and skin showed, that this method furnishes reliable data on molecular transport in these systems. The translational diffusion coefficients are larger for hydrophilic media than for hydrophobic ones, where a good correlation with the dynamic viscosity was found.     

基于有限元方法的双层材料激光超声数值模拟

采用有限元方法数值模拟了单脉冲激光热弹激发双层材料中的超声波,得到了材料的上下表面的应力场分布。通过对铝板中的波形进行快速傅里叶变换得到频率信号,计算出波包群速度,判断出材料中兰姆波的模态。结果表明：受基底影响,在双层材料的上层铝板中得到了三种模态的兰姆波。该研究为复合材料激光超声的应用研究提供了新的途径。     

Induction Method for Electron Spin Resonance Spectrometry

An apparatus is described which uses the unique properties of an H-plane microwave junction to observe electron spin resonance in a manner analogous to the Bloch induction method. The theoretical sensitivity of this technique is expressed as a function of the parameters of the junction and the minimum observable number of unpaired electron spins. This method is compared with cavity techniques and is found to yield high sensitivity for small volume samples.     

Coil and Magnet Design for Nuclear Magnetic Resonance in Inhomogeneous Field

High-resolution nuclear magnetic resonance (NMR) spectrometry is possible in nonhomogeneous magnetic fields-such as those in portable equipment-if the static and the radio-frequency (RF) magnetic fields are perpendicular and correlated in the measurement volume. From the easy-axis rotation theorem and the Amperian currents model, it is possible to exactly match two magnetic fields in two-dimensional systems. We derive a basic probe element that fulfills these conditions. Then we present a portable NMR probe design. The static and RF magnetic fields of the probe are matched on a large volume     

校正激光直写邻近效应的快速方法

针对激光直写中的邻近效应的特点，提出通过直写曝光数据补偿进行光学邻近效应校正的快速，有效方法，并获得了满意的实验结果。