Unidirectional Doppler-free gain and generation in optically pumped lasers

The feasibility of obtaining anisotropic Doppler-free gain and unidirectional generation in optically pumped lasers is studied. The Doppler broadening is compensated due to a pump-induced velocity-dependent light shift of an atomic transition. The gain and spectral characteristics are investigated.     

间接原子吸收法测定饮料蔬果中维生素C

利用三价铁可被维生素C还原为二价铁,铁氰化钾可与Fe2+反应生成腺氏蓝沉淀的原理,建立了原子吸收法间接测定维生素C含量的方法.实验中考察了温度、时间、氧化剂及沉淀剂用量、酸性介质对反应的影响,选取反应在室温下进行,离心时间为5min,浓度为1.0 mg/mL的Fe3+和铁氰化钾溶液各1.00mL,酸性介质为pH=3.5...     

Plasma-based X-ray laser at 21 nm for multidisciplinary applications

An overview of recent advances in applications of currently the most energetic X-ray laser at 21 nm is given. The unique parameters of this half-cavity based X-ray laser such as record output energy of 10 mJ, highly symmetric beam, robustness and reproducibility, have made it possible to carry out a number of multidisciplinary scientific projects featuring novel applications of intense coherent X-ray radiation. Selected results obtained in these experiments are reviewed, including X-ray laser probing of dense plasmas, measurements of transmission of focused soft X-ray radiation at intensities of up to 10¹² W cm^-2, measurements of infrared laser ablation rates of thin foils, and ablative microstructuring of solids.     

A New Discharge Scheme of a Prepulse Plus Two Main Pulses for Capillary-Discharge Soft-X-Ray Laser

Reducing the capillary-discharge current is one way of possibly decreasing the pumping power requirement. We examine the influence of various discharge currents on laser intensity and determine the suitable pre-discharge condition for a 46.9-nm discharge-pumped Ne-like Ar soft-x-ray amplifier. The experimental results show that a high additional pre-pulse current at amplitude of several kA and with a very short duration of several tens of nanosecond can effectively decrease the amplitude of the main discharge current at the lasing time. We propose a new discharge scheme of a pre~pulse plus two main pulses which appears to significantly decrease the requirement for discharge current. This in turn may decrease the pumping power requirement for the capillary discharge laser and can greatly increase laser efficiency.     

基于嵌入式Linux的飞机重心调控系统设计

串口通讯在工业领域有着重要的作用。VC在工业中经常被使用制作各种复杂的监控控制软件,但是VC的图形绘制、API接口功能等存在不方便的地方,本文使用VC的处理能力并借用Qt的图形和其它API接口,这样会大大增加软件开发效率,同时所做软件可移植性变强,可以使用在不同的操作系统中。脉冲发生器在工业系统中运行较多,本文以脉冲发生器为下位机和PC端进行串口通讯的方法。由于工业级软件的设计、应用目前大部分仍以Windows XP为主,所以本文介绍方法主要解决了在低电脑配置PC、低操作系统下灵活使用VC6.0嵌套QT3.3创作出界面强大、稳定的上位机软件。     

羧基化碳纳米管修饰电极的制备及其对Vc的电催化性能

用羧基化碳纳米管修饰玻碳电极制备了一种新型的碳纳米管修饰电极(A)。利用循环伏安,交流阻抗法对A进行了表征。用线性扫描伏安(LSV)法研究了A对Vc的电催化行为,结果表明,在0.1 mol.L-1的醋酸缓冲液(pH5.8)中,当Vc在A表面于-1.0 V电位下富集30 s,电位扫速为100 mV.s-1时,Vc在LSV图上能出现一灵敏的电催化氧化峰,峰电位约为0.149 V;利用该氧化峰可以进行痕量Vc的测定;峰电流与Vc浓度在1.0×10-5mol.L-1～1.0×10-3mol.L-1内成良好线关系,其相关系数为0.996,检出限达1.0×10-6mol.L-1;A稳定性较好,可用于水果和蔬菜中Vc的现场快速检测,回收率96.0%～103.0%。     

Reduced absorption of neon-like bromine X-ray laser radiation in helium

We have measured the absorption of the 19.47-nm neon like bromine (J=2–1) X-ray laser line in low-pressure helium. The experiment was motivated by the coincidence of this line with the low-absorption wing of an autoionizing transition in helium. We observe that, with 1 mbar of helium, the continuum background and another bromine X-ray laser line at 19.82 nm are strongly reduced, enhancing the relative strength of the 19.47-nm laser line. Increasing the helium pressure to 1.5 mbar makes the continuum virtually disappear, resulting in an almost monochromatic emission of the X-ray laser line. An estimate of the absorption cross section for the 19.47-nm line is given as ≈3.9×10^-19 cm² and for the nearby continuum as 0.9–1.3×10^-18 cm². Received: 8 March 1999 / Revised version: 26 April 1999 / Published online: 11 August 1999     

Demonstration of Mo Soft X-Ray Lasers with a Grazing Incidence Pumping Scheme in the XL-II Facility

A Ni-like Mo soft x-ray laser （SXRLs） operating at 18.9nm has been demonstrated by employing a grazing incidence pumping scheme with 120m^3 in the 200ps pre-pulse and 140mJ in the 200fs main pulse. The SXRL gain is estimated to be 1.5-3cm^-1 when a grazing incidence angle of 14° is applied. Numerical simulations are also performed to investigate the dynamics of the ion distribution. It is found that a high intensity at 2.4× 10^14 W/cm^2 of the 200fs main pulse could heat the pre-plasma rapidly to an appropriate temperature for population inversion, and could compensate for the shortage of the total pump energy to a certain extent.     

Multiphoton-induced X-ray emission and amplification from clusters

The development of a unified picture of short-pulse high-intensity multiphoton processes, embracing atoms, molecules, and solids, appears possible through the study of clusters. Of particular significance are possible intra-cluster processes that can influence the mechanism of ionization and lead to the production of inner-shell vacancies. Inner-shell excitation leading to prompt X-ray emission is specifically considered and the treatment leads to the definition of a critical cluster size n _c representing the achievement of maximal X-ray emission from the ensemble. These results suggest the possibility of designing a new class of molecular materials optimized for the efficient production and amplification of X-rays.