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Volume 13 Issue 4
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Original Articles
A Note on Calculation of Threshold Resonance by the Method of Complex Scaling
ZHAO Mei-shan, XIE Xi-shun
Chin. Phys. Lett. 1996, 13 (4): 241-244 .  
Abstract   PDF(pc) (169KB) ( 505 )
A new approach to threshold resonance calculation by the complex scaling method is discussed. Application to scattering over a model potential barrier is presented and compared to a direct quantum scattering calculation.
Square-Preserving and Symplectic Structure and Scheme for Quantum System
DING Pei-zhu, WU Cheng-xun, MU Ying-kui, LI Yan-xin, JIN Ming-Xing
Chin. Phys. Lett. 1996, 13 (4): 245-248 .  
Abstract   PDF(pc) (194KB) ( 416 )
The time-dependent Schrödinger equation is a square-preserving and symplectic (SPS) transformation. The canonical equations of quantum systems are deduced by using eigenfunction expansion. The normal-square of wavefunction of the quantum systems is an invariant integral of the canonical equations and then the symplectic schemes that based on both Cayley transformation and diagonal Padé approximation to exp(x) are also square-preserving. The evaluated example show that the SPS approach is reasonable and effective for solving time-evolution of quantum system.
Escaping from Strange Sets in Discontinuous Circle Map
WANG Bing-hong, HE Da-ren, JI Xi-ping, GUAN Shan, SUN Jian-gang, QU Shi-xian
Chin. Phys. Lett. 1996, 13 (4): 249-252 .  
Abstract   PDF(pc) (191KB) ( 504 )
The leakage of iterations from chaotic attractor near crisis due to dynamical interaction between discontinuity and noninvertibility has been studied. The scaling law of the mean life time is derived analytically. The numerical result shows very good agreement.
Cumulant Correlators and Azimuthal Correlations in PP Collisions at 400 GeV/c
WANG Shao-shun, LI Zu-hao
Chin. Phys. Lett. 1996, 13 (4): 253-256 .  
Abstract   PDF(pc) (184KB) ( 374 )
The cumulant correlators and azimuthal correlations of particles produced in protonproton (PP) collisions at 400 GeV/c are investigated. The second-order cumulant correlators show that the two particle correlation length may be determined by comparing the experimental data with the Monte Carlo events sample which has same multiplicity distributions but no correlation. The azimuthal correlation has also been observed.
Signature Inversion of Yrast Band in Odd-Odd l62Lu Nucleus
ZHANG Yu-hu, ZHOU Xiao-hong, ZHAO Qing-zhong, SUN Xiang-fu, LEI Xiang-guo, GUO Ying-xiang, LIU Zhong, CHEN Xing-feng, ZHU Yong-tai, WEN Shu-xian*, YUAN Guan-jun*, LIU Xiang-an*
Chin. Phys. Lett. 1996, 13 (4): 257-260 .  
Abstract   PDF(pc) (153KB) ( 478 )
High spin states of the odd-odd l62Lu nucleus have been studied via 147Sm(19F,4nγ) reaction at 95MeV beam energy. Level scheme for yrast band based on π [ h11/2]v [i13/2] quasiparticle configuration was established up to Iπ = (23-) for the first time. This band shows the signature inversion in energy before backbending generally appeared in this mass region. It is stressed that the signature splitting in 162Lu is larger than that in 160Tm nucleus.

Tadpole Diagrams and Relativistic Hartree Approximation
WU Shi-shu, YAO Yu-jie
Chin. Phys. Lett. 1996, 13 (4): 261-264 .  
Abstract   PDF(pc) (154KB) ( 449 )
It is pointed out that the infinite series of the tadpole contribution to the baryon self-energy can be summed rigorously and expressed in a simple form. The latter provides a new way for the calculation and explains more clearly the relation between Walecka's mean field theory and the tadpole diagrams.
Dilepton Production of a Baryon-Rich Quark-Gluon Fireball
HE Ze-jun
Chin. Phys. Lett. 1996, 13 (4): 265-268 .  
Abstract   PDF(pc) (218KB) ( 387 )
Based on a relativistic hydrodynamic model, the dilepton production in a baryon-rich quark-gluon fireball is studied. We find that at invariant masses between 2mπ and 1 GeV, with increasing initial baryon density, a characteristic valley and a subsequent peak appear in the total dilepton yield, which signal more uniquely the baryon-rich quark-gluon matter formation and can be tested in future experiments at CERN and

Relativistic Multichannel Theory: Scaling Behavior of Multichannel Quantum Defect Theory Parameters (μα, U) Along the Ne-Like Iso-electronic Sequence
ZOU Yu, TONG Xiao-min, LI Jia-ming
Chin. Phys. Lett. 1996, 13 (4): 269-272 .  
Abstract   PDF(pc) (154KB) ( 421 )
The compact physical parameters (μα, U) in multichannel quantum defect theory (MQDT) can be directly calculated with relativistic multichannel theory (RMCT). Here we report a systematic study of the MQDT parameters (μα, U) with RMCT along the Ne-like iso-electronic sequence (including Ca10+, Fe16+, Ge22+, Ag37+ ions). We find that the physical parameters (μα, U) show a very interesting scaling behavior along the iso-electronic sequence.
Even and Odd Phase Coherent States Associated with the Pegg-Barnett Hermitian Phase Theory
ZHU Jiu-yun, KUANG Le-man
Chin. Phys. Lett. 1996, 13 (4): 273-276 .  
Abstract   PDF(pc) (167KB) ( 807 )
Even and odd phase coherent states associated with the Pegg-Barnett Hermitian phase theory are introduced. Even and odd coherent-state formalism of the Pegg-Barnett phase operator is given in terms of the projection operator in the even and odd coherent-state space. The number-phase uncertainty relation is investigated for these states.
Quantum Cryptography Using Coherent State
ZHANG Xiao-yu, GUO Guang-can
Chin. Phys. Lett. 1996, 13 (4): 277-280 .  
Abstract   PDF(pc) (191KB) ( 509 )
Quantum cryptography is a new way to distribute keys, which can detect any eavesdropping. Quantum cryptography using single particle or weak light pulse has been discussed in some early papers, but it is difficult to transmit such single particle or weak light pulse. We propose a scheme of quantum key distribution using coherent State |α > and |α + Δα>. We also discuss its feasibility and security, and give an experimental realization of this scheme.
A Self-Excitation Double Pathway Relaxation Oscillational Model of Rare-Earth-Doped Laser
WANG Zhong-he, ZHANG Guang-yin
Chin. Phys. Lett. 1996, 13 (4): 281-284 .  
Abstract   PDF(pc) (192KB) ( 458 )
A self-excitation double pathway relaxation oscillation mechanism to deal with the self-pulsing output of upconversion laser with rare-earth ions as the active material is raised. The reabsorption of the laser signal, which causes self-excitation of system and two-pathway transition of system, plays a role of adjusting Q, and causes the oscillation output of laser. A qualitative analysis to the appearance of self-pulsing output of rare-earth-doped laser is given.
Direction-Dependent Switching in Nonlinear Chirped Gratings
LIU Jun-min, LIAO Chang-jun, LIU Song-hao, XU Wen-cheng
Chin. Phys. Lett. 1996, 13 (4): 285-288 .  
Abstract   PDF(pc) (220KB) ( 502 )
Chirped gratings with uniform Kerr nonlinearity are numerically demonstrated to have direction-dependent switching behavior, which is caused by the different energy storage between the two incident directions. This effect can find useful applications such as optical diode and optical switch-isolator.
Precipitation of Cu and Ni on Frank-Type Partial Dislocations in Czochralski-Grown Silicon
SHEN Bo, ZHANG Rong, SHI Yi, ZHENG You-dou, T. Sekiguchi*, K. Sumino*
Chin. Phys. Lett. 1996, 13 (4): 289-292 .  
Abstract   PDF(pc) (399KB) ( 463 )
Precipitation behaviors of Cu and Ni on Frank-type partial dislocations in Czochralski-grown silicon are investigated. It is found that Cu develops precipitate colonies in the region away from Frank partials and does not decorate Frank partials when the specimens are cooled slowly, while Ni decorates them although the concentration of Ni is lower than that of Cu in the specimens. The results indicate that Ni impurity is easier to decorate Frank partials than Cu impurity in Si.

High Pressure Raman Study of Phase Transitions on Solid Benzene Using Raman Notch Filter Set
XU Li-wen, WANG Ru-ju, CHEN Liang-chen
Chin. Phys. Lett. 1996, 13 (4): 293-297 .  
Abstract   PDF(pc) (217KB) ( 408 )
A high-throughput Raman notch filter set has been manufactured and used to collect the Raman scattering signals of pressure-induced phase transitions of solid benzene in a diamond anvil cell up to 15 GPa at room temperature. The changes in the profiles as well as the frequencies of Raman scattering spectra are observed and enable us to determine the phase transition.
Effect of Electric Field on the Electron-Surface Optical Phonon Scattering Rates in Quantum Wires
CHANG Kai, WANG Ruo-zhen, MA Ben-kun
Chin. Phys. Lett. 1996, 13 (4): 297-300 .  
Abstract   PDF(pc) (226KB) ( 467 )
By using the variational method and the dielectric continuum model, we investigate the effect of electric field on the intrasubband scattering rates of electron-surface optical phonon. The results show that the scattering rates tend to increase with the electric field strength. These scattering rates become significant for wide quantum well wire and sufficiently high fields.
Threshold Lowering and by Intensity and Efficiency Enhancement by Dopants in Polymer Emitting Diodes
ZHANG Zhi-lin, JIANG Xue-yin, XU Shao-hong, T. Nagatomo*, O. Omoto*
Chin. Phys. Lett. 1996, 13 (4): 301-304 .  
Abstract   PDF(pc) (239KB) ( 474 )
A new method to increase the luminance and quantum efficiency of polymer light emitting diodes with a lower threshold voltage has been reported. The threshold voltage, luminance and quantum efficiency have been significantly improved by doping certain dopants with a lower highest occupied molecular orbital (HOMO) level into the hole transporting layer. A high performance device has been achieved by addition of the perylene and triphenylamine as a dopant into poly(N-vinylcarbazole). The luminance and quantum efficiency increase by 2-3 times in comparison with the undoped device, reaching 10000cd/m2 in luminance and 0.58% in quantum efficiency, while threshold voltage is reduced to one half value. The energy diagram has been obtained by measuring the HOMO levels and band gap values. Based on this, the carriers injection and balance between electrons and holes as well as the action of dopant are discussed.

Reactive Sputter Deposition of Carbon Nitride Films by Using Hollow-Cathode Discharge
ZHAO Jing, KANG Ning, XU Ji-ren
Chin. Phys. Lett. 1996, 13 (4): 305-308 .  
Abstract   PDF(pc) (178KB) ( 465 )
Carbon nitride films have been prepared by reactive sputtering using hollow cathode discharge. Auger spectra show that the nitrogen content is about 20-25at.% in the bulk. Infrared (IR) spectra display three broad absorption bands. After heating treatment, changes of IR spectra suggest that the nitrogen incorporating in the bonding network of amorphous is thermally stable and hydrogen content decreases.
Diffuse Reflectance Fourier Transform Infrared Spectrometry of BN Films Deposited on Steels by Remote Microwave Plasma CVD from Borazine
LEI Ming-kai, MA Teng-cai, V. A. Emel kin*
Chin. Phys. Lett. 1996, 13 (4): 309-313 .  
Abstract   PDF(pc) (234KB) ( 797 )
The diffuse reflectance Fourier transform infrared spectra of the boron nitride (BN) films deposited on steels by remote microwave plasma chemical vapour deposition (CVD) from borazine with nitrogen, hydrogen and argon were investigated in the wavenumber range of 400-4000cm-1. It was found that the cubic BN formation depends on production of the intermediate species of cyclotriborazane ((BH2NH2)3) and its dehydrogenation. The structural bonds of cyclotriborazane are similar to that of cubic BN. Optimum conditions for deposited BN films were found to be the borazine-nitrogen mixture at the substrate temperature of 550°C. The BN films were a mixture of crystalline cubic BN accounting for the major content and hexagonal BN with relatively low hydrogen content.

Time-Resolved Measurement of Nonradiative Processes by Using Laser Interferometry
FU Shao-wei, WU Zong-sen, GAN Chang-ming, ZHANG Shu-yi, ZHANG Zhi*, CHEN Hui-lan*
Chin. Phys. Lett. 1996, 13 (4): 313-316 .  
Abstract   PDF(pc) (200KB) ( 451 )
Photoacoustic signals generated by nonradiative processes of photo-initiated chemical reactions in solutions have been detected by a laser heterodyne interferometer with high sensitivity and wide band. This technique can accurately carry out the time-resolved measurement of transient processes in nanosecond scale. The experimental results and theoretical calculations for probing some fast chemical reactions are described.

Primordial Black Holes and Cosmic String Loop
CHENG Hong-bo*, LI Xin-zhou
Chin. Phys. Lett. 1996, 13 (4): 317-320 .  
Abstract   PDF(pc) (189KB) ( 531 )
The elliptic loop equation of cosmic string is studied in the Minkowski space and during the radiation-dominated era in the Robertson- Walker universe. A remarkable fact about this equation is that a loop may never contract to one with a Schwarzschild radius, if it is sufficiently non-circular.
20 articles