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J/ψ →γBB Decays and the Quark Pair Creation Model
PING Rong-Gang, JIANG Huan-Qing, , SHEN Peng-Nian, , ZOU Bing-Song, ,
Chin. Phys. Lett. 2002, 19 (11):
1592-1595
.
We generalize the quark-pair creation model to a study of the radiative decays J/ψ →γBB by assuming that the u, d, or s quark pairs are created with the same interaction strength. From the calculation of the ratio of the decay widths Γ(J/ψ →γpp)/Γ(J/ψ →γpp), we extract the quark-pair creation strength gI = 15.40 GeV. Based on the SU(6) spin-flavor basis and the “uds”basis, the radiative decay branching ratios containing strange baryons are evaluated. Measurements for these decay widths from the BESII data are suggested.
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Possible 1d5/2 and 2s1/2 Level Inversion in the Proton-Rich Nucleus 23Al
ZHANG Hu-Yong, SHEN Wen-Qing, REN Zhong-Zhou, MA Yu-Gang, CAI Xiang-Zhou, ZHONG Chen, WEI Yi-Bin, CHEN Jin-Gen
Chin. Phys. Lett. 2002, 19 (11):
1599-1601
.
The discovered proton halo nucleus of 23Al is investigated in the nonlinear relativistic mean-field (RMF) model with deformation using the NL075 force parameter. It is shown that there is an energy inversion between the (5/2)+(202) and (1/2)+(211) orbital in the 23Al nucleus, which may produce a large enhancement of the reaction cross section compared with the neighboring nuclei. Meanwhile, the NL075 force parameter may be better than the other RMF parameters for calculation of large deformed nucleus 23Al.
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Role of Advanced Refueling and Heating on Edge Reynolds Stress-Induced Poloidal Flow in HL-1M
HONG Wen-Yu, WANG En-Yao, LI Qiang, CAO Jian-Yong, YAN Long-Wen
Chin. Phys. Lett. 2002, 19 (11):
1643-1645
.
The radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been measured in the plasma boundary region of the HL-1M tokamak using a multiarray of Mach/Langmuir probes. In the experiments of Ohmic discharge, lower hybrid current drive, supersonic molecular beam injection (SMBI) and multi-shot pellet injection, the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The radial profile changes of the Reynolds stress and poloidal flow velocity Vpol with lower hybrid wave injection power and SMBI injection are obtained. The results indicate that the sheared poloidal flow can be generated in tokamak plasma due to the radially varying Reynolds stress.
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Kinetics and Mechanism of Nanostructures in Oxidation of
Si1-xGex Alloys
HUANG Wei-Qi, CAI Shao-Hong
Chin. Phys. Lett. 2002, 19 (11):
1657-1659
.
We investigate the oxidation behaviour of Si1-xGex alloys (x= 0.05, 0.15, and 0.25). The oxidation of SiGe films with different compositions was carried out in O2 (dry) atmosphere at 800 °C , 900 °C, and 1000 °C, respectively, for various lengths of time. The thickness and property of nanoparticle and nanolayer in oxide films and germanium segregation in oxidation of SiGe alloys are measured by using a high precision ellipsometer. The results are in good agreement with the Rutherford backscattering spectrometry, profile dektak instrument and high-resolution scanning transmission electron microscopy. We found that the Ge content in the oxide layer increases with the Ge content in SiGe alloys, the Ge content in the oxide film decreases with the increasing oxidation temperature and time. Rejection of Ge results in piling up of Ge at the interface between the growing SiO2
of nanostructure of oxide and Ge segregation in oxidation of
Si1-xGex alloys.
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Correction to the Metal-Insulator Transition Temperature due to
Cation Size and Strain Effects for Colossal Magnetoresistance
Perovskites
YUAN Song-Liu, LIU Jie, XIA Zheng-Cai, PENG Gang, TANG Jie, ZHANG Guo-Hong, ZHANG Li-Jiang, FENG Wen, LI Zhong-Yi, YANG Ying-Ping, LIU Li, XIONG Cao-Shui
Chin. Phys. Lett. 2002, 19 (11):
1675-1678
.
A phenomenological expression of the metal-insulator transition temperature is proposed for AMnO3 manganese perovskites by taking into account the distortion of Mn-O-Mn bond due to A-cation size and the strain-dependent effect due to performed Jahn-Teller distortions, independently. Using reasonable physical parameters, the calculated results give excellent agreement with experimental data obtained in polycrystalline samples of La2/3(Ca1-xBax)1/3MnO3, providing a strong support to this approach.
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Distribution Function of Mesoscopic Hopping Conductance
HE Li-Qun, Eugene Kogan, Moshe Kaveh, Shlomo Havlin, Nehemia Schartz, LUO Dawei
Chin. Phys. Lett. 2002, 19 (11):
1683-1686
.
We study mesoscopic hopping conductance by computer simulation
distribution functions (DF). It is found that the distributions obtained by choosing randomly the chemical potentials (for a fixed impurity configuration), which corresponds to a typical experimental situation, coincide with those obtained when both impurity configuration and chemical potential are chosen randomly, in agreement with the ergodicity hypothesis. The DFs in shape obtained for one-dimensional systems are found to be quite close to the predictions of the theory by Raikh and Ruzin. For the two-dimensional case, the DFs both for a narrow system and thin film look to be similar (and close to the one-dimensional case). The distribution function for the conductance of the square sample is nearly Gaussian.
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Carrier Transport Behaviour of Molecularly Doped Poly (N-Vinylcarbozole) in Polymer Light-Emitting Diodes
CHEN Xiao-Hong, , XU Zheng, HOU Yan-Bing, LIU Shu-Man, TENG Feng, XU Xu-Rong,
Chin. Phys. Lett. 2002, 19 (11):
1697-1699
.
Single-layer polymer light-emitting diodes (PLEDs) are prepared from blends of poly (N-vinylcarbozole) (PVK) doped with tris (8-hydroxy-quinoline) aluminum (Alq3) of 2 wt% (sample a) and 0.2 wt% (sample b). The onset of PVK transient electroluminescence (EL) is delayed with respect to that of Alq3 in sample a under pulsed excitation, While the EL onset of Alq3 and PVK in sample b are simultaneous. The total carrier mobility of Alq3-rich regions in sample a is larger than that of PVK-rich regions. However, the total carrier mobility is homogenous in sample b. The phase image of atomic force microscopy and photoluminescence spectra of sample a and sample b indicate that the separated phase of samples a and b exists in PVK-rich regions and Alq3-rich regions. The variance of the doping concentration and separated phase in blends results in the different carrier transport mobility of Alq3-rich regions and PVK-rich regions.
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Optical Constants of Palladium Phthalocyanine Derivative Thin Films
WU Yi-Qun, GU Dong-Hong, GAN Fu-Xi, WANG Jun-Dong, CHEN Nai-Sheng
Chin. Phys. Lett. 2002, 19 (11):
1700-1703
.
Ellipsometric parameters of a series of spin-coating thin films of palladium phthalocyanine derivatives with bromine and tetraalkoxyl substitutes [PdPc(OC8H17 4Brm, m = 0,2,3,4] are determined from a rotating analyser-polarizer type of scanning ellipsometer. The optical, dielectric constants and absorption coefficients of the films in the 500-800 nm wavelength region are reported. The results show that refractive index N (N = n-k), dielectric constant ε (ε = ε1 - ε2) and absorption coefficient α in the region 500-800 nm are influenced by bromine atom substituted on the conjugated phthalocyanine ring regularly. It is found that there is approximately linear relationship between the resonance absorption wavelengths of the films and the number of bromine atoms substituted on the phthalocyanine ring.
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Photoluminescence Properties of Silicon Nanowires and Carbon Nanotube-Silicon Nanowire Composite Arrays
LI Meng-Ke, LU Mei, KONG Ling-Bin, WANG Cheng-Wei, GUO Xin-Yong, LI Hu-Lin
Chin. Phys. Lett. 2002, 19 (11):
1703-1706
.
Composite arrays of multi-wall carbon nanotubes (MWNTs) and silicon nanowires (SiNWs) are fabricated by means of the chemical vapor deposition method in porous anodic aluminum oxide (AAO) templates. The results of the scanning electron microscopy, high-resolution transmission electron microscopy, and transmission electron microscopy have shown that SiNWs are successful nested or filled in the hollow cavities of synthesized MWNTs array in AAO templates to form MWNTs-SiNWs composite arrays. The photoluminescence (PL) intensity degradation and a blue shift of PL peak position, usually created from the chemical instability of the SiNWs surface, are decreased and eliminated clearly in the composite arrays. The composite arrays of MWNTs-SiNWs exhibit more enhanced intensity and stability of PL performance than the SiNWs arrays deposited in AAO templates.
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Characterization of Growth Hillocks on the Surface of High-Pressure Synthetic Diamonds
YIN Long-Wei, LI Mu-Sen, YUAN Quan, XU Bin, HAO Zhao-Yin
Chin. Phys. Lett. 2002, 19 (11):
1707-1710
.
Diamond crystals, with dimensions of about 0.5-0.6 mm, were synthesized in the presence of Fe-Ni and Fe-Ni-Si catalyst solvents under high-pressure-high-temperature (HPHT) conditions. The as-known dendritic pattern was clearly seen on the (111) or (100) planes of diamond single crystals grown using Fe-Ni as a catalyst solvent. However, the conventional dendritic pattern was not observed in diamonds grown in the presence of Fe-Ni-Si alloy catalyst. Trigonal-type, pyramid-type, polygonal-type, and rectangular-type growth hillocks were clearly observed on the (111) and (100) surfaces of diamonds grown from the Fe-Ni-Si-C system, and the density of the hillocks is very higher at some position. Clear successive growth layers can also be found on the (111) planes of the high-pressure diamond single crystals grown in the presence of Fe-Ni Si alloy catalyst. The growth hillocks distributing on the (111) and (100) planes of the diamonds generally occur on or near growth steps, and some of the hillocks terminate at certain solid inclusions and voids. Growth hillocks on the (111) and (100) surfaces directly indicate the spiral growth mechanism under high temperature-high pressure (HPHT). A possible formation process for growth hillocks is proposed.
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Comparisons of Structural and Optical Properties of ZnO Films
Grown on Sapphire and Si (001)
QIU Dong-Jiang, WU Hui-Zhen, XU Xiao-Ling, CHEN Nai-Bo
Chin. Phys. Lett. 2002, 19 (11):
1714-1717
.
Zinc oxide films were grown on sapphire and Si (001) substrates by reactive electron beam evaporation at low substrate temperatures. Atomic force microscopy (AFM), x-ray diffraction (XRD), and photoluminescence excitation (PLE) are employed to characterize the as-grown films. The AFM measurements have shown that all of the ZnO films present the pillar-like growth properties, but the dimensional uniformity of the ZnO crystal pillars grown on sapphire was better than
that on Si (001). The XRD results indicated that the prepared ZnO films both on sapphire and Si (001) were all highly c-axis oriented, their linewidth of ZnO (002) are only 0.19° and 0.28°, respectively. The PLE characterizations revealed the continuum absorption of the samples grown on sapphire. However, in the PLE spectra of the ZnO films grown on Si(001) substrates, a broad peak appears at the high energy region, which indicates the formation of ZnO quantum dot structures on Si(001).
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Geometrical Deviation and Residual Strain in Novel Silicon-on-Aluminum-Nitride Bonded Wafers
MEN Chuan-Ling, XU Zheng, WU Yan-Jun, AN Zheng-Hu, XIE Xin-Yun, LIN Cheng-Lu
Chin. Phys. Lett. 2002, 19 (11):
1718-1720
.
Aluminum nitride (AlN), with much higher thermal conductivity, is considered to be an excellent alternative to the SiO2 layer in traditional silicon-on-insulator (SOI) materials. The silicon-on-aluminum-nitride (SOAN) structure was fabricated by the smart-cut process to alleviate the self-heating effects for traditional SOI. The convergent beam Kikuchi line diffraction pattern results show that some rotational misalignment exists when two wafers are bonded, which is about 3°. The high-resolution x-ray diffraction result indicates that, before annealed at high temperature, the residual lattice strain in the top silicon layer is tensile. After annealed at 1100°C for an hour, the strain in the top Si decreases greatly and reverses from tensile to the slightly compressive as a result of viscous flow of AlN.
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Evolutionary Population Synthesis for Single Stellar Populations
ZHANG Feng-Hui, HAN Zhan-Wen, LI Li-Fang, Jarrod R. Hurley
Chin. Phys. Lett. 2002, 19 (11):
1734-1737
.
Using the evolutionary population synthesis technique, we present the latest integrated colours for instantaneous burst single stellar populations (SSPs) of different metallicities and we investigate their colour evolution. Different from the previous research we adopt the stellar evolutionary models that employ, amongst other things, recent opacities and a revised equation of state (EOS), and include evolutionary processes such as convective overshooting, thermal pulses and dredge-up. The models are used in the convenient form of analytic fitting functions. In addition, we use the BaSeL model for the library of stellar spectra. This model provides an extensive low-resolution theoretical flux distribution and UBVRIJHKLM colours, which have been calibrated empirically or semi empirically, for a wide range of stellar parameters.
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50 articles
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