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Volume 14 Issue 7
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Original Articles
Phase Probability Density Function in Two-Mode Fock Space
FAN Hong-yi, YANG Zhen-shan
Chin. Phys. Lett. 1997, 14 (7): 481-484 .  
Abstract   PDF(pc) (178KB) ( 486 )
Based on the newly found representation |η > = exp[-(|η|2/2) +η a + η*b - a b ]|00> in which the phase operator √(a+b )l(a+b) corresponding to Shapiro-Wagner phase measurement scheme manifestly exhibits its phase behavior, we construct the phase probability density function in the two-mode Fock space, which provides an alternative approach for analysing the phase properties of optical fields.

Generation of Multi-atom Entangled States via the Raman Atom-Cavity-Field Interaction
ZHENG Shi-biao, GUO Guang-can
Chin. Phys. Lett. 1997, 14 (7): 485-487 .  
Abstract   PDF(pc) (153KB) ( 522 )
A scheme is presented for preparing multi-atom entangled states based on the Raman atom-cavity-field interaction. After several degenerate Λ-type three-level atoms interact with an appropriately prepared single-mode cavity field through Raman coupling, a two-level atom, resonant with the cavity, is sent through the cavity and a Ramsey zone. The detection of the two-level atom leaves the Λ-type atoms in an entangled state.

Scheme for Reducing Decoherence in Quantum Computer Memory by Transformation to the Coherence-Preserving States
DUAN Lu-ming, GUO Guang-can
Chin. Phys. Lett. 1997, 14 (7): 488-491 .  
Abstract   PDF(pc) (220KB) ( 1417 )
If quantum bits (qubits) couple to the Same environment, it has been found the qubits decohere coherently. An interesting result from this phenomenon is that, for a kind of input states, i. e., the coherence-preserving states, coherence of the qubits can be preserved perfectly in quantum memory. In this paper, we propose a feasible scheme to transform an arbitrary unknown input state to the corresponding coherence-preserving state. The transformed state undergoes no decoherence in the noisy memory and, after that, it can be transformed back into the original state with decoherence much reduced. This scheme involves the use of an analogy of the ideas of quantum teleportation.
Exact (3+1)-Dimensional, 2-Soliton Solutions to the Einstein Gravitational Field Equation
AU Chi, TANG Meng-xi
Chin. Phys. Lett. 1997, 14 (7): 492-494 .  
Abstract   PDF(pc) (122KB) ( 426 )
A set of exact (3+1)-dimensional cylindrically symmetric 2-soliton solutions with three arbitrary functions to the Einstein gravitational field equation is found. Their physical properties, such as nontriviality, propagation and positive definiteness of energy density, are discussed.
Quantum Corrections to the Entropy of the Black Hole with a Global Monopole or a Cosmic String
JING Ji-liang
Chin. Phys. Lett. 1997, 14 (7): 495-498 .  
Abstract   PDF(pc) (233KB) ( 432 )
The quantum corrections to the entropy of the static black holes with a global monopole or a cosmic string are studied by two methods: the brick wall and the Euclidean path integral. If we ignore the usual contribution from the vacuum surrounding the system, then the two approaches give the same results. The quantum corrections for the static black holes consist of two parts: One is quadratically divergent term which takes the geometric character. The other is a logarithmically divergent term which is not proportional to the horizon area. The renormalization of the quadratically and logarithmically divergent is also investigated.
Control of Unstable Periodic Orbit by Means of Projective Operator Method
LIU Zong-hua, CHEN Shi-gang
Chin. Phys. Lett. 1997, 14 (7): 499-502 .  
Abstract   PDF(pc) (169KB) ( 374 )
We define the projective operators for controlling unstable periodic orbit(UPO), and project the eigenvectors of Jacobian matrix of a system in the direction of trajectory and in the direction perpendicular to the trajectory. Then the two eigenvalues in the perpendicular direction are changed to negative ones by adjusting the controlling parameter. So the control of UPO can be implemented. It is also shown that the procedure is effective even in the presence of noise.
Systematics of β and γ Parameters of O(6)-Like Nuclei in the Interacting Boson Model
WANG Bao-lin
Chin. Phys. Lett. 1997, 14 (7): 503-506 .  
Abstract   PDF(pc) (235KB) ( 441 )
By comparing quadrupole moments between the interacting boson model (IBM) and the collective model, a simple calculation for the triaxial deformation parameters β and γ in the O(6)-like nuclei is presented, based on the intrinsic frame in the IBM. The systematics of the β and γ are studied. The realistic cases are calculated for the even-even Xe, Ba, and Ce isotopes, and the smooth dependences of the strength ratios θ3/ and the effective charges e2 on the proton and neutron boson numbers Nπ and Nv are discovered.


A New Determination of 208Hg Half-Life
ZHANG Li, ZHAO Jin-hua, ZHENG Ji-wen, WANG Ji-cheng, YANG Yong-feng, QIN Zhi, GUO Tian-rui
Chin. Phys. Lett. 1997, 14 (7): 507-509 .  
Abstract   PDF(pc) (190KB) ( 428 )
A specific detection system devoted to the detection of weak γ-activities from neutron-rich isotopes in an element-separated source was developed, and successfully used in a new determination of the half-life of the recently identified heavy neutron-rich nuclide 208Hg. This newly measured half-life is 41+5-4min, in agreement with the earlier one of 42+23-11 min obtained by radiochemical milking method, but experimental precision was improved.
Kaon-Source Size in Relativistic Nucleus-Nucleus Collisions
ZHENG Yu-ming, CHU Zi-li, Osamu Miyamura, Kenji Kumagai
Chin. Phys. Lett. 1997, 14 (7): 510-512 .  
Abstract   PDF(pc) (162KB) ( 355 )
We analyze the two-kaon Bose-Einstein correlation in the reactions of 160A GeV/c Pb+Pb within an event generator URASiMA. The apparent radius of kaon-source is extracted. The theoretical result agrees quite well with the preliminary data of NA44.
Study of C70 Adsorbed on Silver Surface by Surface Enhanced Raman Scattering
HUANG Ya-bin, MO Yu-jun, G. Mattei, M. Pagnnane, XIE Si-shen
Chin. Phys. Lett. 1997, 14 (7): 513-516 .  
Abstract   PDF(pc) (227KB) ( 465 )
Twelve new features from our Raman measurements of C70 have been observed by using the silver surface enhanced Raman scattering substrate with very high enhanced factor and highly sensitive Raman set. The results and discussion in this letter would make new knowledge to vibration modes of C70. The experimental data of the study confirm the validity of Jishi's calculation with a small error.

Evolution of Field Entropy in the Formation of a Photon-Number State
LIU Zheng-dong, ZENG Liang
Chin. Phys. Lett. 1997, 14 (7): 517-520 .  
Abstract   PDF(pc) (251KB) ( 337 )
In the formation of a photon-number state in a micromaser, the evolution of field entropy versus the injected atom number is studied with and without the rotating-wave approximation, and the results in these two different cases are compared. An entropy-decreasing system and the quantum oscillation induced by virtual photons are discussed.
A Quantum Cryptography Key Distribution Way Using Orthogonal States
SHI Bao-sen, GUO Guang-can
Chin. Phys. Lett. 1997, 14 (7): 521-523 .  
Abstract   PDF(pc) (144KB) ( 397 )
A different quantum cryptography key distribution way based on the orthogonal states is presented in the system, instead of using two sources [Phys. Rev. Lett. 75 (1995) 1239], only one source and one channel are needed to produce two orthogonal states by modulating phase. It is very easy to realize this method in practice.
Quantum Nondemolition Measurements for Phonons by Using Squeezing Stokes Light
CHAI Jin-hua, GUO Guang-can
Chin. Phys. Lett. 1997, 14 (7): 524-527 .  
Abstract   PDF(pc) (213KB) ( 399 )
A scheme of quantum nondemolition (QND) measurement is proposed for phonons in a Raman-active crystal by using a beam of squeezed Stokes light. The results of the theoretical calculation show that the QND measurements for the quadrature component of the phonons can be performed.

Cluster Model for p-Type Doping of ZnSe
REN Tian-ling, ZHU Jia-lin, XIONG Jia-jiong, DUAN Wen-hui, WANG Fu-he
Chin. Phys. Lett. 1997, 14 (7): 528-530 .  
Abstract   PDF(pc) (196KB) ( 479 )
Cluster model with DV-Xα method is used to study the structural and electronic properties of the p-type doping of ZnSe. It is found that there is Jahn-Teller distortion for P doping and almost no Jahn-Teller distortion for N doping, and that the impurity levels with respect to the maximum of valence band are 118 and 96meV for N and P doping, respectively. The reasons why N can serve as a better dopant than P for p-type ZnSe are discussed.
Oxygen Ion Beam and Plasma Induced Blood Compatibility of Polyetherurethane
LI De-jun, CUI Fu-zhai, FENG Qing-ling, ZHAO Jie
Chin. Phys. Lett. 1997, 14 (7): 531-534 .  
Abstract   PDF(pc) (268KB) ( 351 )
Surface blood compatibility of ion beam and plasma treatment on polyetherurethane has been studied. O+ implantation was performed at 80keV with various doses. O2 plasma treatment was carried out at 100 W with various exposure times. The results indicated that surface anticogulability was enhanced in varying degrees and anticalcific behavior was not decreased. X-ray photoelectron spectroscopy and electron spin resonance analysis showed that the two methods not only broke some chemical bonds, but also produced some new N-O and C-O bonds and radicals in the surface, which affected the surface biomedical behavior.

Characterization of High-Energy-Heavy-Ion-Induced Defects in GaAs by Positron Annihilation
ZHU Sheng-yun, LUO Qi, FAN Zhi-guo, WANG Chun-rui, ZHENG Sheng-nan, GOU Zhen-hui, LI An-li, QIAN Jia-yu
Chin. Phys. Lett. 1997, 14 (7): 535-537 .  
Abstract   PDF(pc) (206KB) ( 507 )
The defects induced by 64 MeV 19F ion irradiation to a Auence of 4.3 ×1016/cm2 are investigated in GaAs by positron annihilation lifetime technique. Di-vacancies are created by the irradiation. The formation of tri- and quadri-vacancies is observed during thermal annealing. The di-, tri-and quadri-vacancies are annealed away at 350, 550 and 800°C, respectively.
Dynamic Failure of Shock-Loaded Glass
HE Hong-liang, JIN Xiao-gang, JING Fu-qian, G. I. Kanel
Chin. Phys. Lett. 1997, 14 (7): 538-541 .  
Abstract   PDF(pc) (204KB) ( 467 )
Failure wave generations on both impacted surface and internal surface inside the sample have been observed for K9 glass under planar shock wave loading, which demonstrates that formation of failure wave is a process related to the surface microcracks nuclei developing. Based on these observations, a hypothesis is suggested that the large local strains resulting from the rearrangement of SiO4 tetrahedral within the permanent densification region behind the shock wave front and then strains releasing due to the surface microcracks developing could be responsible for the failure wave generation.
Electronic Structure of Equilibrium-State TiNx Films
ZHANG Zhi-peng, SHEN Yao-wen, XU Wei, HUANG Mei-chun
Chin. Phys. Lett. 1997, 14 (7): 542-545 .  
Abstract   PDF(pc) (204KB) ( 402 )
By using LMTO-ASA method and supercell approach, the self-consistent band structures for α-Ti, ε-Ti2N, and δ-TiN have been calculated. Moreover, α-Ti, ε-Ti2N, and δ-TiN were taken as three samples corresponding to TiNx films for x = 0, 0.5, 1.0. Then, according to the phase diagram of Ti-N and statistical supercell method, we have, for the first time to our knowledge, calculated the electronic structures of equilibrium-state TiNx films for all compositions of x < 1.0.
Highly Oriented HgBaCaCuO Superconducting Thin Films Prepared by Laser Ablation
YU Yang, SHAO Hui-min, ZENG Zhao-yang, SUN Ai-min, QIN Meng-jun, REN Chong, XU Xiao-nong, DING Shi-ying, JIN Xin, YAO Xi-xian, ZHOU Jun, JI Zheng-ming, YANG Sheng-zu, ZHANG Wen-lan
Chin. Phys. Lett. 1997, 14 (7): 546-548 .  
Abstract   PDF(pc) (238KB) ( 466 )
Pb-doped HgBa2CaCu2Oy films were prepared on the (100) SrTiO3 substrate by using laser ablation followed by post-Hg-vapor annealing. These films are dominated by c-axis-oriented Hg-1212 phase as indicated by x-ray diffraction and electromagnetic measurements. The transition temperature Tc0 is 110 K. The critical current density Jc achieved 106 A/cm2 at 77K and zero applied field.
Luminescence from Si/SiO2 with Si Implantation
LAN Ai-dong, LIU Bai-xin, BAI Xin-de
Chin. Phys. Lett. 1997, 14 (7): 549-552 .  
Abstract   PDF(pc) (237KB) ( 343 )
Silicon single crystals with a SiO2 overlayer of various thicknesses ( 1000-6000Å ) were implanted by 120 and 160keV Si-ions to doses in a range of (0.5-1.0)x1017cm-2 to study the visible light emission in their as-implanted and post-annealed states. An emission band peaked around 2.0eV was visible in the photoluminescence (PL) spectra of all the as-implanted samples. After post-annealing at 1100°C in a flowing N2 gas, it was found that a visible band peaked in the range of 1.7eV is detectable from all the samples and that the PL intensity exihibits a correlation with the oxygen concentration in the implanted region. Possible mechanisms responsible for the observed light emission were also discussed.
Studies of the Gd Overlayer on Cr by Synchrotron Radiation Photoemission
ZHANG Fa-pei, XU Peng-shou, XU Shi-hong, LU Er-dong, YU Xiao-jiang, ZHANG Xin-yi
Chin. Phys. Lett. 1997, 14 (7): 553-556 .  
Abstract   PDF(pc) (248KB) ( 457 )
The formation of Gd/Cr interface, the growth mechanism and electronic structure of Gd over-layers were investigated by synchrotron radiation photoemission. It is shown that Gd adatoms interact with the Cr substrate weakly. A lower deposition rate of the Gd overlayer (l.0Å/min) favors the smooth growth of Gd/Cr interface. However, higher deposition rate (6.0Å/min) leads to the cluster growth of the Gd overlayer and the presence of a “two-peak” feature of Gd 4f emission. We correlate this feature with the different coordination number of surface atoms derived from cluster- induced surface roughness.
Gamma-Ray Bursts from Discharges in Plasmas
LI Ti-pei, WU Mei
Chin. Phys. Lett. 1997, 14 (7): 557-560 .  
Abstract   PDF(pc) (258KB) ( 347 )
We show that large-voltage and high-temperature pinch plasma columns can generate hard x-ray and γ-ray flashes with energy spectra and spectral evolution characteristics consistent with those observed in γ-ray bursts.
22 articles