Current Issue

Volume 11 Issue 9
Online Date:
Previous Issue    Next Issue
Original Articles
Angular Distribution of Electrons Following Photoionization of n sns 1S0 Rydberg States in the Alkaline-Earth Atoms
DAI Changjian (C.J.Dai)
Chin. Phys. Lett. 1994, 11 (9): 529-532 .  
Abstract   PDF(pc) (159KB) ( 406 )
A new characterization of the angular distribution of electron ejected from n'pns autoionizing states in the alkaline-earth atoms has been carried out from the most general expression of differential cross section of photoabsorption. The same approach may be extended to more complicated cases where the traditional treatment becomes invalid. The comparison between the two methods is presented.
Theoretical Simulations of Ni-Like Laser Lines
CHEN Guoxin, FANG Quanyu, CAI Wei
Chin. Phys. Lett. 1994, 11 (9): 533-536 .  
Abstract   PDF(pc) (210KB) ( 445 )
Multi-configuration Dirac-Fock and configuration interaction calculations in the extensive average level version with the inclusion of the transverse (Breit) interaction and low orders quantum electrodynamics have been carried out for the wavelengths of five Ni-like laser lines. The ab initio results have been adjusted along the iso-electronic sequence and predict the wavelengths. The predicted results have been compared and agree with available experimental values and may serve as road sign for experimentalists.
Stopping Power of Compounds for l6O and l9F Ions
WU Zeqing, LU Xiting, JIN Changwen, ZHENG Tao, XIA Zonghuang, LIU Hongtao, JIANG Dongxing, YE Yanlin
Chin. Phys. Lett. 1994, 11 (9): 537-540 .  
Abstract   PDF(pc) (163KB) ( 506 )
The stopping powers of CaF2 and MoO3 for l6O and l9F were measured with heavy-substrate Rutherford backscattering technique. The present results are compared with the prediction of Bragg's rule, and strong deviation was observed. The experimental error is 5% or so.
Laser Cooling and Deceleration of Neutral Atoms by Red-Shifted Diffuse Light
CHEN Hongxin, CAI Weiquan, LIU Liang, SHU Wei, LI Fosheng, WANG Yuzhu
Chin. Phys. Lett. 1994, 11 (9): 541-544 .  
Abstract   PDF(pc) (220KB) ( 461 )
We report a cooling and deceleration experiment of a thermal beam by using a nearly resonant red-shifted diffuse light in an optical integral sphere cavity. By using of this red-shifted diffuse light, the velocity of a part of thermal sodium atoms is cooled to 380m/s and the velocity width of cooled atoms is about 18m/s. The mechanism of this kind of laser cooling and the experimental results are discussed.
A Unified description of Atomic distortion in Strong Converging Laser Field
ZHANG Wenqing
Chin. Phys. Lett. 1994, 11 (9): 545-547 .  
Abstract   PDF(pc) (127KB) ( 419 )
We give a unified theoretical frame, which introduces the self-consistent theory and quantum defect theory into the area of atom-radiation interaction to describe the atomic distortion in strong converging laser field. It can be used to study the energy shift and wavefunction stretching of realistic multielectronic atom.
New Method to Increase the Parameter Detection Sensitivity of Ultrashort Optical Pulse
YU Hong, ZHANG Mingde, MAO Qinghe, DIN Dong, YANG Xianglin
Chin. Phys. Lett. 1994, 11 (9): 548-550 .  
Abstract   PDF(pc) (141KB) ( 397 )
An autocorrelation system by second harmonic generation with organic crystal POM is described. Picosecond optical pulses produced by a 1.55μm gain-switching distributed feedback laser diode have been measured and the detection sensitivity of the system of 70μW for average power is obtained.
High-Efficiency Second Harmonic Generation of a Pulsed Ti : Al2O3 Laser with β-BaB2O4 Crystal
LIU Xiang, DENG Daoqun, ZHANG Yufei, XU Zuyan
Chin. Phys. Lett. 1994, 11 (9): 551-553 .  
Abstract   PDF(pc) (148KB) ( 548 )
Tunable blue radiation with a tuning range of 340-460nm has been generated using a β-BaB2O4 crystal for external frequency doubling of a ns-pulsed Ti : Al2O3 laser. By pumping the Ti: sapphire with 94mJ/pulse of energy from the second harmonic of a Q-switched Nd: YAG laser, as much as 5.4mJ/pulse at 390nm with a bandwidth of 0.02nm was obtained. This represents an infrared to blue conversion efficiency of 36% and a total conversion (from 532nm to blue) of 5.7%.
XUV Spectroscopy of Subpicosecond Laser Produced Plasmas
JIANG Zhiming (Z. Jiang)*, J. C. Kieffer, M. Chaker
Chin. Phys. Lett. 1994, 11 (9): 554-557 .  
Abstract   PDF(pc) (281KB) ( 388 )
The keV and XUV spectra of plasmas produced by the interaction of a laser pulse of various duration and wavelengths with, a solid Al target are compared and discussed. Drastic decrease of the XUV emission from the high ionization states was observed with the shortest pulses (500fs) and the shortest wavelength (0.5μm), which may be due to rapid cooling and quenching of ultrashort-lived and initially ultra-dense plasmas.
High-Power-Density Plasma Deposition of Diamond-Like Carbons Films
YAN Pengxun, YANG Si-ze, YANG Jie, LI Qing, LI Bing, LIU Chizi, CHEN Xishen
Chin. Phys. Lett. 1994, 11 (9): 558-560 .  
Abstract   PDF(pc) (148KB) ( 533 )
We present a new method utilizing a high-power-density plasma for depositing diamond-like carbon (DLC) films. The main advantage of this technique is the possibility that films with good adhesion to the substrate can be prepared under room temperature and low pressure. The DLC films are deposited on the silicon substrate successfully. The structure of the DLC films was characterized by high energy electron diffraction, scanning electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, and infrared absorption spectrum.
Ni-B Nanometer Particles Observed by Scanning Tunneling Microscopy
LI Xiangyang, CHENG Huansheng, YANG Fujia, YANG Xinju, YANG Jun
Chin. Phys. Lett. 1994, 11 (9): 561-564 .  
Abstract   PDF(pc) (230KB) ( 487 )
The samples of the Ni-B nanometer particles which were suitable for scanning tunneling microscopy (STM) have been prepared and observed. Our experimental results suggest that the vertical height of the nanometer particles imaged by the STM has strongly related to the method of the sample preparation. For the Ni-B nanometer particle the water and impurity layer adsorbed to the particle surface played an important role in the conduction mechanism. At last alcohol can be used as a tool to disperse the nanometer particles on the highly oriented pyrolytic graphite support.
Measurement of Enthalpy Relaxation in a Metallic Glass Pd77.5 Cu6.0 Si16.5
DING Xingzhao, HE Yizhen
Chin. Phys. Lett. 1994, 11 (9): 565-568 .  
Abstract   PDF(pc) (178KB) ( 398 )
Enthalpy relaxation in amorphous Pd77.5 Cu6.0 Si16.5 in sub-Tg temperature region was studied by differential scanning calorimetry (DSC). Enthalpy change due to annealing, which was measured by deducting the effect of glass transition, increased gradually to a saturated value with increasing annealing time (ta). At lower temperatures, enthalpy relaxation exhibited two-stage in ta dependence.
New Method for Determining the Shock Temperature of Metals
TANG Wenhui, JING Fuqian, HU Jinbiao, ZHANG Ruoqi
Chin. Phys. Lett. 1994, 11 (9): 569-572 .  
Abstract   PDF(pc) (189KB) ( 377 )
Traditionally, shock temperature determination of metals needs to do a two-step calculation from the measured thermal radiation history. In this paper, however, we present some experimental events which make it possible to deduce the release temperature directly from the measured interface radiation history record.
A New Method for Studying the Distribution of Induced Defects in Potential Wells in a-Si : H/a-SiNx : H Multilayer
WANG Zhichao, GUO Shengkang, CAO Guorong, CHEN Cai, SUN Meixiang
Chin. Phys. Lett. 1994, 11 (9): 573-576 .  
Abstract   PDF(pc) (211KB) ( 408 )
The induced defects and their distribution in a-Si: H/a-SiNx : H multilayers can be determined by use of electromagnetic technique. It is found that the distributions of the induced defects in the interface regions on both sides of the a-Si:H sublayer are asymmetric and related to the growth direction of the film; a large number of induced defects exist in the interface region away from substrate, but few or no in the interface region near substrate.
Diffusion of Silver in Nanometer Ni-B Amorphous Alloy
LI Xiangyang, CHENG Huansheng, HE Wenquan, YANG Fujia
Chin. Phys. Lett. 1994, 11 (9): 577-580 .  
Abstract   PDF(pc) (203KB) ( 490 )
Diffusion of Ag in nanometer Ni-B amorphous alloy, has been studied by heavy-ion Rutherford backscattering spectroscopy. The values of the diffusion coefficient which were found at 293, 323 and 373K, are 3.5x10-l6, 4.3 x10-l5 and 5.0x10-l4 cm2/s, respectively. Moreover, small values for the activation energy, 0.58 eV, and the pre-exponential factor of the diffusion coefficient, 3.9 x10-16 cm2/s , were derived from Arrhenius plot. Finally, a possible free volume controlled diffusion mechanism was discussed.
Size Effects on the Crystallite Structure and Phase Transition in Lanthanaum-Modified Lead Titanate Nanocrystals
WANG Xiaohui, WANG Zichen, ZHAO Muyu, MENG Jinfang*, LI Jiangping*, ZOU Guangtian*
Chin. Phys. Lett. 1994, 11 (9): 581-584 .  
Abstract   PDF(pc) (186KB) ( 454 )
The size effects on the crystallite structure, Raman spectra as well as phase tian-sition in lanthanum-modified lead titanate Pb1-xLaxTi1-3/4xO3(x=0.14) (PLT14) nanocrystalline powders were investigated. The results show that with decreasing grain size, the crystallite structure changes from tetragonal perovskite phase to cubic perovskite phase; the soft mode frequency at room temperature decreases, and disappears when the grain size is as small as 19nm; the phase transition temperature from ferroelectric to paraelectric shifts towards a low temperature region. The phase transition in nanocrystalline PLT14 is a second order one, which is confirmed by its dielectric constant measurement.
Analysis of Quasielastic Light Scattering in Ferroelectric Liquid Crystal
ZHANG Ping, YIN Zhen, ZHANG Mingsheng, HUANG Qiang
Chin. Phys. Lett. 1994, 11 (9): 585-588 .  
Abstract   PDF(pc) (203KB) ( 388 )
Temperature dependence of Raman spectra of ferroelectric liquid crystal MBOPDOB is examined in spectral region 0-30cm-1 with spectral emphasis on the quasielastic light scattering near solid-Sm C* transition. The quasielastic components are well fitted to Debye-type susceptibility function. With increase of temperature the inverse of the relaxation time T linearly goes to zero in the temperature range below the transition, manifesting a critical slowing-down. The relaxation time keeps same big value in the Sm C* phase as that at the transition point owing to long orientational relaxation in the liquid phase.
Piezoresistive Effect of Diamond Films Produced by dc Plasma CVD
WANG Wanlu, LIAO Kejun
Chin. Phys. Lett. 1994, 11 (9): 589-592 .  
Abstract   PDF(pc) (193KB) ( 527 )
The piezoresistive effect of polycrystalline p-type diamond films formed by dc plasma chemical vapour deposition has been investigated. The gauge factor is about 116 at 500 microstrains at room temperature, and strongly increases with increasing temperature, exceeding that of polycrystalline- and single-silicon. The origin of the piezoresistivity in boron doped polycrystalline diamond films may be ascribed to strain-induced shift of the boron acceptor level and grain boundaries.
17 articles