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Total Quantum Statistical Entropy of Reissner-Nordstrom Black
Holes: Scalar Field Case
XU Dian-Yan
Chin. Phys. Lett. 2001, 18 (10):
1312-1315
.
The total quantum statistical entropy of Reissner-Nordstrom (RN) black holes is evaluated. The spacetime of the black holes is divided into three regions-region 1,( r > ro), region 2, ( ro > r > ri), and region 3, (ri > r > 0 ), where ro is the radius of the outer event horizon, and ri is the radius of the inner event horizon. The total quantum statistical entropy of RN black holes is S = S1 + S2 + S3, where Si, ( i = 1,2,3) is the entropy, contributed by region Si (i = 1,2,3). The detailed calculation shows that S2 ≈ 0. S1 = (π2/45) [ kbAo/ε2β3], S3 = -(π2/45) [kbAi/ε2β3], where Ao and Ai are, respectively, the area of the outer and inner event horizons. Thus, as ri approaches ro, in the extreme case the total quantum statistical entropy of RN black holes approaches zero.
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Search for Signature Inversion in πi13/2 vi13/2 Band in Odd-Odd 178Ir
ZHANG Yu-Hu, T. Hayakawa, M. Oshima, Y. Toh, J. Katakura, Y. Hatsukawa, M. Matsuda, N. Shinohara, T. Ishii, H. Kusakari, M. Sugawara, T. Komatsubara, K. Furuno
Chin. Phys. Lett. 2001, 18 (10):
1323-1326
.
Search for the πi13/2 vi13/2 band in 178Ir have been conducted through the 152Sm(31P,5nγ)178Ir reaction and the excitation functions, x-γ and γ-γ-t coincidence measurements. Five rotational bands have been newly identified. The low-spin signature inversion in the πi13/2 vi13/2 band has been confirmed by the observations of linking transitions and signature crossing at I = 25.5ħ. The inversion phenomenon in πh11/2 vi13/2, πh9/2 vi13/2, and πh13/2 vi13/2 structures in 178Ir provides a unique testing ground for different theoretical interpretations.
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Laser Amplification Mechanism in an Nd3+-Doped
Polymer Optical Fiber
GUO Yang, ZHENG Xing, MINNG Hai, ZHANG Qi-Jin
Chin. Phys. Lett. 2001, 18 (10):
1337-1340
.
The Judd-Ofelt theory was applied to optical-absorption transitions in an Nd3+-doped polymer optical fiber to obtain intensity parameters (Ω2 = 0.83 x 10-20cm2, Ω4 = 1.64 x 10-20cm2, Ω6 = 4.04 x 10-20cm2) the radiative lifetime (371 μs) and quantum efficiency (0.73) of the 4G5/2level, from which we found that the transition probability from 4G5/2 to 4I9/2(Aij = 1995.7 s-1) is higher than others. Thus, in the polymer system, the traditional four-level laser system for the Nd3+ was substituted by a three-level system. Furthermore, we have calculate the emission cross section(σeij =2.45 x 10-21cm2), and solved the differential equations of the single-pass gain. In comparsion with the case of the inorganic optical fiber, an increased saturated intensity is observed.
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Ultrasonic Properties of the MgB2 Superconductor
LI Shao-Chun, WANG Ru-Ju, LI Feng-Ying, LIU Zhen-Xing, ZHU Jia-Lin, YU Ri-Cheng, JIN Chang-Qing
Chin. Phys. Lett. 2001, 18 (10):
1369-1370
.
The sound velocities of longitudinal and shear waves are measured on polycrystalline MgB2 superconductor with Tc of 39K. The specimen used in the experiments is pressed and heated using the MgB2 powder. The elastic moduli, Debye temperature and specific heat at room temperature are obtained based on sound velocity data. The results indicate that the velocities are much higher than those in the usual materials, while elastic constants remain reasonably soft, which may be due to the high transition temperature of the MgB2 superconductor.
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Effects of Polarization on Super-hot Electron Generation in Femtosecond Laser-Plasma Interaction
ZHANG Ping, LIANG Tian-Jiao, CHEN Li-Ming, LI Yu-Tong, CHEN De-Bao, LI Zu-Hao, HE Jing-Tang, WEI Zhi-Yi, WANG Long, TAMG Xiao-Wei, ZHANG Jie
Chin. Phys. Lett. 2001, 18 (10):
1374-1376
.
The effects of laser polarization on super-hot electron (>100 keV) generation have been studied in the interaction of femtosecond laser light (800nm, 150fs, 6 x 1015W.cm-2) with a pre-formed plasma from a slab Cu target. For p-polarized laser pulses, high-energy γ-rays of the energy ~ 400keV were detected, the electron temperatures deduced from the γ-ray spectra were 66 and 52keV, respectively, in normal and reflective directions of the solid target, and hot electrons were emitted out of the plasma mainly in the normal direction. In contrast, there were nearly no γ-rays >100keV found for s-polarized laser pulses, The hot electron temperature was 26keV and the emission of hot electrons was parallel to the laser field. The superposition of resonant field with electrostatic field excited by escaping electrons may contribute to the high-energy γ-ray or super-hot electron (> 100keV) generation.
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Microstructure Transition of Liquid Metal Al During Heating and Cooling Processes
LIU Rang-Su, LIU Hai-Rong, ZHENG Cai-Xing, LU Xiao-Yong, PENG Ping, LI Ji-Yong
Chin. Phys. Lett. 2001, 18 (10):
1383-1385
.
A simulation study of the transition properties of microstructures of liquid metal Al during heating and cooling processes has been performed by the molecular dynamics method. It is demonstrated that in the temperature range of 1800--350K, the 1551, 1541, 1431, 1311, 1321, and 1422 bond types represented by the Honeycutt-Andersen index play an important role. Especially, the 1551 bond type plays a leading role and is the decisive factor for the change of the second peak of the pair distribution function from a smooth sine peak into two split secondary peaks via a platform during all the processes of microstructure transitions. From the variation curve of the
1551 bond type, it can be clearly seen that there are five rapidly changing ranges corresponding qualitatively to the critical transition points of microstructures of the system detected experimentally.
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Structure and Photoluminescence of InGaAs Quantum Dots Formed on an InAlAs Wetting Layer
ZHANG Yuan-Chang, HUANG Chang-Jun, YE Xiao-Ling, XU Bo, DING Ding, WANG Ji-Zheng, LI Yue-Fa, LIU Feng-Qi, WANG Zhan-Guo
Chin. Phys. Lett. 2001, 18 (10):
1411-1414
.
We have developed a new self-assembled quantum dot system where InGaAs dots are formed on an InAlAs wetting layer and embedded in the GaAs matrix. The structure is realized by special sample designation and demonstrated by low-temperature photoluminescence measurements. In contrast to the traditional InAs/GaAs quantum dots dominated by the ensemble effect, the temperature dependence of photoluminescence of such a quantum dot structure behaves as decoupled quantum dots. This can be attributed to the enhanced potential confinement for the dots provided by a higher-energy barrier in the wetting layer.
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Surface Acoustic Wave Velocity and Electromechanical Coupling
Coefficient of GaN Grown on (0001) Sapphire by Metal-Organic Vapor Phase Epitaxy
CHEN Zhen, LU Da-Cheng, WANG Xiao-Hui, LIU Xiang-Lin, HAN Pei-De, YUAN Hai-Rong, WANG Du, WANG Zhan-Guo, HE Shi-Tang, LI Hong-Lang, YAN Li, CHEN Xiao-Yang
Chin. Phys. Lett. 2001, 18 (10):
1418-1419
.
High-quality and high-resistivity GaN films were grown on (0001) sapphire face by metal-organic vapor phase epitaxy. To measure the surface acoustic wave properties accurately, we deposited metallized interdigital trans-ducers on the GaN surface. The acoustic surface wave velocity and electromechanical coupling coefficient were measured, respectively, to be 5667m/s and 1.9% by the pulse method.
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40 articles
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