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Development of β-NMR and β-NQR
ZHOU Dong-Mei, ZHENG Yong-Nan, ZHU Jia-Zheng, XU Yong-Jun, DU En-Peng, WANG Zhi-Qiang, Luo Hai-Long, YUAN Da-Qing, RONG Chao-Fan, M. Mihara, M. Fukuda, K. Matsuta, T. Minamisono, ZHU Sheng-Yun
Chin. Phys. Lett. 2003, 20 (10):
1698-1701
.
The β-NMR (nuclear magnetic resonance) and β-NQR (nuclear quadrupole resonance) technique and its experimental set-up have been developed for the first time in China. The lifetime, magnetic moment and spin polarization of 12B were determined. The experimental results show the reliability of this newly developed β-NMR and β-NQR set-up.
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Ab-Initio Study of Electronic Structure and Magnetic Properties of Pipz-H2[MnF4(HF2)]
YAO Kai-Lun, WANG Li-Qiang, LIU Zu-Li, ZOU Wei-Dong, LUO Shi-Jun, ZU Feng-Xia, ZHU Lin
Chin. Phys. Lett. 2003, 20 (10):
1710-1713
.
The full-potential linearized augmented plane wave method was applied to study the electronic and the magnetic properties of the compound pipz-H2[MnF4(HF2)](pipz=piperazine). The band structure, the total density of states, the partial density of states and the electron density were calculated to explain the electronic and the magnetic properties of pipz-H2[MnF4(HF2)] in the ferromagnetic state. It is found that the magnetic moment of the molecule mainly comes from the Mn atoms with partial contribution from the F atoms. The symmetrical σ/σ bonds via H atoms along Mn-F-H-F-Mn chains and the weak direct-exchange interaction between F(2), F(3) and Mn atoms have effect on the electronic structure and the magnetism of pipz-H2[MnF4(HF2)].
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Optically Forbidden Excitations of 3s Electron of Argon by Fast Electron Impact
ZHU Lin-Fan, CHENG Hua-Dong, LIU Xiao-Jing, TIAN Peng, YUAN Zhen-Sheng, LI Wen-Bin, XU Ke-Zun
Chin. Phys. Lett. 2003, 20 (10):
1718-1720
.
The electron energy loss spectrum of argon in the energy region of 24.5-30.5 eV was measured at 2.5 keV impact energy. The line profile parameters of the optically forbidden excitations of 3s-1 ns (n = 4-6) and 3s-1 nd (n = 3-7) of argon, i.e., Eγ, Γ, q and μ, were determined.
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Epoxy Resin-Photopolymer Composite with None-Shrinkage for
Volume Holography
LIU Guo-Dong, HE Qing-Sheng, LUO Shou-Jun, WU Min-Xian, JIN Guo-Fan, SHI Meng-Quan, WU Fei-Peng
Chin. Phys. Lett. 2003, 20 (10):
1733-1735
.
A novel photopolymer storage medium for holographic storage is presented. In particular, the refractive index of the monomer methyl methacrylate is much lower than that of the binder epoxy resin solidified by m-xylylenediamine, and the material can be developed into samples with dimension stability and high optical quality and thickness of several millimeters or more. Some none-polymeric macromolecule impurity is uniformly mixed into the medium to aid the monomer diffusing and to enhance the diffraction efficiency. A holographic recording medium of 0.8 mm thickness has been fabricated, and relative theoretical analysis and experiments are presented.
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Diode-Pumped Passively Q-Switched Yb:YAG Microchip Laser with a GaAs as Saturable Absorber
{ZHANG Qiu-Lin, FENG Bao-Hua, ZHANG Dong-Xiang, FU Pan-Ming, ZHANG Zhi-Guo, ZHAO Zhi-Wei, DENG Pei-Zhen, XU Jun, XU Xiao-Dong, WANG Yong-Gang, MA Xiao-Yu
Chin. Phys. Lett. 2003, 20 (10):
1741-1743
.
A passively Q-switched Yb: YAG microchip laser has been constructed by using a doped GaAs as the saturable absorber as well as the output coupler. At 13.5 W of pump power the device produces high-quality 3.4μJ 52 ns pulses at 1030 nm with a pulse repetition rate of 7.8 kHz in a TEM00-mode.
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Large Enhancement of Optical Nonlinearities of New Organophosphorus Fullerene Derivative
LIU Zhi-Bo, TIAN Jian-Guo, ZANG Wei-Ping, ZHOU Wen-Yuan, ZHANG Chun-Ping, ZHENG Jian-Yu, ZHOU Ying-Chun, XU Hua
Chin. Phys. Lett. 2003, 20 (10):
1744-1747
.
Optical nonlinearities of new organophosphorus fullerene derivative were determined by the Z-scan method with a pulsed Q-switch Nd:YAG laser at 532 nm. The experimental results demonstrated that the derivative has much larger excited-states nonlinear absorption and nonlinear refraction than C60. A five-level model was utilized to fit the experiemntal data, and a good agreement is reached. Some parameters such as excited-state absorption cross and refraction cross were obtained. To our knowledge, the excited-state cross section of new organophosphorus fullerene derivative and its effective ratio to the ground-state cross section are the largest values among the fullerene derivatives reported to date.
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Visualizations of Light-induced Refractive Index Changes in Photorefractive Crystals Employing Digital Holography
ZHAO Jian-Lin, ZHANG Peng, ZHOU Jian-Bo, ANG De-Xing, YANG Dong-Sheng, LI En-Pu
Chin. Phys. Lett. 2003, 20 (10):
1748-1751
.
We propose a novel approach to visualize the light-induced refractive index changes in photorefractive crystals employing digital holography. The holograms formed in a Mach-Zehnder interferometer are recorded by a two-dimensional CCD camera. From these holograms, the phase differences, which contain the information of the index changes in photorefractive crystals, are determined by utilizing digital holographic interferometry. Then the two-dimensional visualizations of index changes in the crystals can be obtained. This method is successfully emonstrated in LiNbO3:Fe, KNSBN:Ce and SBN:Cr crystals.
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Efficient Dual-LBO Second-Harmonic Generation by Using a Polarization Modulation Configuration
BI Yong, SUN Zhi-Pei, LI Rui-Ning, ZHANG Ying, YAO Ai-Yun, LIN Xue-Chun, XU Zu-Yan, WANG Fang
Chin. Phys. Lett. 2003, 20 (10):
1755-1758
.
We analyse the relationship of conversion efficiency with the inter-crystal phase shift by the heuristic theory and propose a novel configuration of two cascaded nonlinear crystals for the second-harmonic generation with the polarization modulation. With this configuration, 70% external doubling efficiency is obtained, which is, to the best of our knowledge, the highest conversion efficiency with LBO crystal external frequency doubling. This configuration provides a simple and effective method to improve the second harmonic conversion efficiency.
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Ultrafast Third-Order Nonlinear Optical Response of Organic-Inorganic Hybrid Materials (C19H25N2)7Hn[P2Mo18-nVnO62]
XIANG Hong, GAO Li-Hua, WANG Ke-Zhi, WANG Zhen-Wei, LI Zhi, HUANG Wen-Tao, YANG Hong, GONG Qi-Huang
Chin. Phys. Lett. 2003, 20 (10):
1759-1762
.
We have measured the third-order optical nonlinearity of the organic-inorganic hybrid materials of supermolecules (C19H25N2)7Hn[P2Mo18-nVnO62] (n =1, 2, 4, 5) and their reactants (C19H25N2)Br and Hn+6[P2Mo18-nVnO62] by using the ultrafast optical Kerr effect at 830 nm wavelength, with time resolution of 115 fs. By comparing the γ values of the supermolecules and their reactants, it is concluded that the charge-transfer enhanced remarkably the third-order optical nonlinearity of the compounds. With the increment of the number of the vanadium atoms, the electron distribution changed strongly and the γ value decreased dramatically.
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A Novel Bi-wavelength Method for Accurately Measuring Gain and Noise Characteristics of an Erbium-Doped Fibre Amplifier for Multi-Channel Wavelength Division Multiplexing Transmission
LIU Yan-Ge, MENG Hong-Yun, YUAN Shu-Zhong, TIAN Jian-Guo, KAI Gui-Yun, DONG Xiao-Yi
Chin. Phys. Lett. 2003, 20 (10):
1777-1780
.
Gain and noise figure (NF) are the most important two parameters of an erbium-doped fibre amplifier (EDFA) for a multi-channel wavelength division multiplexing (WDM) transmission system. A simple bi-wavelength method for accurate gain and NF spectrum measurement of EDFA for WDM applications is proposed. A saturating input signal, whose power equals to the sum of all the WDM signal power and whose wavelength is determined by the channel numbers, and the wavelength of the WDM input signals saturates the EDFA in a degree as the same as the WDM signals input. Meanwhile, a small power probe signal scans and measures the gain and the NF value at every wavelength of the WDM input signals. Investigative results by numerical simulation show that the gain and the NF spectra measured by this method have good agreement with the real spectra of the WDM signal input in a large total input power range. The maximum errors of the gain and the NF are less than 0.2 dB and 0.16 dB, respectively, for a 50-channel input case. The method is competent for the accurate gain and the NF spectrum measurement of the fibre preamplifier and the line-amplifier for WDM applications and has the advantages of simplicity, convenience and easy implement.
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Characteristics of Microwave Discharge in a Modified Surfaguide with a Large Diameter
DING Zhen-Feng, P. Tristant, J. Desmaison, DONG Chuang, WANG You-Nian
Chin. Phys. Lett. 2003, 20 (10):
1792-1794
.
The characteristics of the microwave discharge are studied in a modified surfaguide with a large diameter. Experimental results show that there exist three discharging modes, one is the plasma mode, and the others are the waveguide modes. The discharge can jump between one of the waveguide modes and the plasma mode, and the corresponding hysteresis loop is influenced by the discharging pressure. In the higher pressure region, the hysteresis loop is wide enough so that the discharge in each mode is stable. In the middle pressure region, the discharge becomes unstable as a result of the hysteresis loop being sufficiently narrow. When the gas pressure is further decreased, the plasma mode disappears, while the mode jumps between the two waveguide modes always appear and are stable in the discharge region we have explored.
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Neutral Beam Injection Experiments in the HL-1M Tokamak
YAN Long-Wen, LEI Guang-Jiu, ZHONG Guang-Wu, JIANG Tao, ZHOU Yan, JIANG Shao-Feng, DING Xuan-Tong, ZHOU Cai-Pin, LIU Yong
Chin. Phys. Lett. 2003, 20 (10):
1795-1798
.
Neutral beam injection (NBI) experiments have been carried out with two operation modes of a bucket ion source in the HL-1M tokamak. During the first mode, more than 30% rise in ion temperature above the Ohmic level is routinely achieved after NBI power about 0.5 MW is injected. Ion temperature only increases 20-30% for the second operation mode, which is often limited by current termination. The heating effects of the NBI have been analysed experimentally and theoretically. The performance of the NBI system is well described.
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Conditions for the Observation of Two Ion-Acoustic Waves via Thosmon Scattering
ZHENG Jian, HU Guang-Yue, WANG Zhe-Bin, YU Chang-Xuan, LIU Wan-Dong
Chin. Phys. Lett. 2003, 20 (10):
1799-1802
.
Observation of two ion-acoustic waves via Thomson scattering can provide precise measurements of plasma parameters. The conditions for the observation of two ion-acoustic modes in a two-ion plasma are discussed. The ratio of electron temperature Te to ion temperature Ti is the critical parameter for the presence of two ion-acoustic modes, which should be in the range of 4/ZL Te/Ti 2AH/ZHAL, where ZL,H are the charge states of light and heavy ions, and AL,H are the atomic numbers of light and heavy ions, respectively. As the temperature ratio varies in this range, the concentration of heavy ions must increase with the ratio Te/Ti so that the two ion-acoustic modes can have the same fluctuation levels.
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Resonant Absorption Mechanical Spectrometer and Its Applications in Solids
ZHANG Jin-Xiu, GONG Kang, XIONG Xiao-Min, DING Xi-Dong
Chin. Phys. Lett. 2003, 20 (10):
1807-1810
.
An improved apparatus is developed from Ke-pendulum. This new apparatus, resonant absorption mechanical spectrometer (RAMS), can measure the internal friction of solids under a forced vibration mode and the measuring frequency can change quasi-continually from a frequency that is much lower than the resonant frequency of the pendulum system, fr, to the one that is much higher than fr. The internal friction measurement is able to cover the frequency range from 10-3Hz to kHz. The measurement method and the calculation formula of the internal friction measured by a RAMS in the full frequency range are derived. A series of resonant absorption peaks are observed in copper, aluminum, zinc, iron samples by the RAMS. The resonant absorption characteristics of the copper sample are studied in details. The experimental results indicate that the position (frequency) of the resonant absorption peaks are independent of the resonant frequency of the pendulum system. The reality of resonant absorption mechanical spectra is discussed and an inference based on the experimental results is presented such that the RAMS is able to characterize some feature of solid materials.
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Effects of Laser-Induced Heating on the Photoinduced Birefringence in Azobenzene-Side-Chain Copolymer
YANG Jun, MING Hai, ZHANG Jiang-Ying, WANG Pei, LANG Jian-Jing, LU Yong-Hua, LIU Jian, ZHANG Qi-Jin
Chin. Phys. Lett. 2003, 20 (10):
1826-1828
.
The photoinduced birefringence was observed in the polymer poly[2-(4-(4-cyanophenyl) diazenyl phenyloxy) ethoxyl methacrylate] with a cw 532 nm laser. The azobenzene polymer character has been studied under the conditions of various illuminating time and light intensities. By analysing the processes of reorientation, the effect of laser-induced heating has been introduced to the buildup of photoinduced birefringence in azobenzene-side-chain copolymer. The curves for the buildup of birefringence were fitted with a modified function, i.e., biexponential curves and Gaussian curves. The relationship among all the parameters has also been presented. With the modified fitting function, we obtain a better fitting result.
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Injection Efficiency of Spin-Polarized Quasiparticles in Y-Ba-Cu-O Thin Film
YANG Ming, CAO Chun-Hai, ZHANG Shi-Yuan, YANG Sen-Zu, CUI Xu-Gao, YOU Li-Xing, JI Zheng-Ming, KANG Lin, XU Wei-Wei
Chin. Phys. Lett. 2003, 20 (10):
1848-1851
.
The injection efficiency of spin-polarized quasiparticles in a superconducting Y-Ba-Cu-O (YBCO) film is investigated by means of current injection into the Nd0.7Sr0.3MnO3/SrTiO3/YBa2Cu3O7-δ heterostructures. We have successfully prepared six injection junction windows in the YBCO thin film strip, which are all 5 μm wide, but 80 μm, 40 μm, 20 μm, 10 μm, 5 μm, and 2 μm long, respectively. At 16 K, our YBCO thin film strip (80 nm thick) has Jc = 2 x 105A/cm2. Under the spin-polarized injection current of Iinj = 0.5 mA, with the decrease of injection junction length L, injection efficiency η(η ΔJc/ΔJinj; ΔJc: the suppression of critical current density due to finite ΔJinj increases gradually, till L is not more than 20 μm. In that case, η hardly varies with the change of L, reaching up to about 6. We think that these results are related to the spin diffusion length of spin-polarized quasiparticles in the superconducting thin film. In our heterostructures, the YBCO thin film keeps good superconductivity and the injection junction windows are of proper size, therefore, we have obtained relatively high injection efficiency of spin-polarized quasi-particles.
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Realization of Red-Organic-Light Emitting Diode by Introducing the Double Emitting Zone
JIANG Wen-Long, HOU Jing-Ying, ZHAO Yi, LIU Shi-Yong
Chin. Phys. Lett. 2003, 20 (10):
1861-1863
.
A saturated red-organic-light emitting diode (OLED) has been realized by doping an emitting material both in the hole-transporting layer (HTL) and the electron-transporting layer (ETL) to form double emitting zone. The red dopant, 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), was doped into the N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) layer and the tris (8-quinolinolate) aluminum (Alq3) layer, both of which act as the emitting layers. The optimal device, with a structure of ITO/CuPc/NPB/NPB:DCJTB/Alq3:DCJTB/Alq3/LiF/Al, showed good chromaticity coordinates (x = 0.63, y = 0.36) at 8 V. Uniquely, the current efficiency of the device was relatively independent of the drive voltage in a wide range from 8 V to 20 V. That may be helpful to ameliorate the lifetime of the organic electroluminescent devices and to adjust the gray-scale for the future full-color display panel.
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Low-Temperature Growth of Polycrystalline Silicon Films by
SiCl4/H2 rf Plasma Enhanced Chemical Vapor Deposition
LIN Xuan-Ying, HUANG Chuang-Jun, LIN Kui-Xun, YU Yun-Peng, YU Chu-Ying, CHI Ling-Fei
Chin. Phys. Lett. 2003, 20 (10):
1879-1882
.
Polycrystalline silicon film was directly fabricated at 200°C by the conventional plasma enhanced chemical vapor deposition method from SiCl4 with H2 dilution. The crystallization depends strongly on the deposition power. The maximum crystallinity and the crystalline grain size are over 80% and 200-500 nm, respectively. The results of energy dispersive spectroscopy and infrared spectroscopy measurements demonstrate that the film is mostly composed of silicon, without impurities such as Cl, N, C and bonded H. It is suggested that the crystallization at such a low temperature originates from the effects of chlorine, i.e., in-situ chemical etching, in-situ chemical cleaning, and the detachment of bonded H.
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70 articles
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