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Decay of the 67-μs Isomer in 142Pm
LIU Min-Liang, ZHANG Yu-Hu, ZHOU Xiao-Hong, GUO Ying-Xiang, LEI Xiang-Guo, LIU Zhong, HE Jian-Jun, WEN Shu-Xian, WU Xiao-Guang, YUAN Guan-Jun
Chin. Phys. Lett. 2004, 21 (4):
626-628
.
Excited states in 142Pm are investigated via the 128Te(19F, 5n)142Pm reaction at beam energies from 75 to 95 MeV by using techniques of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation function, X-γ and γ-γ-t coincidences are performed with 10 BGO(AC)HPGe detectors. Decay of the previously known 67-μs isomer in 142Pm is observed and added into the new level scheme. This isomer is definitely placed at the excitation energy of 2828.5 keV. The spin of this isomer is suggested to be 13ħ according to the measured γ-ray anisotropies.
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A New Possible Probe for Investigating the Exotic Structure of Neutron-Rich Nuclei by Using the Hanbury-Brown-Twiss Method
WEI Yi-Bin, MA Yu-Gang, SHEN Wen-Qing, MA Guo-Liang, WANG Kun, CAI Xiang-Zhou, ZHONG Chen, GUO Wei, CHEN Jin-Gen, ZHOU Xing-Fei
Chin. Phys. Lett. 2004, 21 (4):
629-631
.
Hanbury-Brown-Twiss (HBT) results of the nucleon--nucleon correlation function have been presented for the nuclear reactions with neutron-rich projectiles using an event-generator, i.e. the isospin-dependent quantum molecular dynamics model. A good agreement of our calculation for the two-halo-neutron correlation function of 11Li with the experimental data has been reached. In addition, we explore the relationship between the single-neutron separation energy and the strength of the HBT results. It is feasible to investigate the exotic structure of neutron-rich nuclei with the HBT method.
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Analytic Continuation in the Coupling Constant Method for the Dirac Equation
ZHANG Shi-Sheng, GUO Jian-You, ZHANG Shuang-Quan, MENG Jie,
Chin. Phys. Lett. 2004, 21 (4):
632-635
.
On the basis of the Dirac equation, the analytic continuation in the coupling constant method is employed to investigate the energies and widths of single-particle resonant in square-well, harmonic-oscillator, and Woods-Saxon potentials. The influences of the coupling constant interval and the Padé approximant order are analysed. It is shown that, by properly choosing the coupling constant interval and the Padé approximant order, stable and convergent energies and widths of single-particle resonant states can be obtained, which makes the application of the analytic continuation in the coupling constant for the relativistic mean field theory possible.
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Odd--Even Effects of the Survival Probability for Superheavy Compound Nuclei
LI Wen-Fei, , WANG Zhen-Zhong, XU Hu-Shan, MA Yue, ZHANG Hong-Fei, ZUO Wei, , LI Jun-Qing, , WANG Nan, ZHAO En-Guang, W. Scheid
Chin. Phys. Lett. 2004, 21 (4):
636-639
.
The survival probability of the superheavy compound nuclei with Z = 114 is studied with the statistical model. It is found that the survival probability shows drastic odd-even effects. The odd-A compound nuclei have higher survival probability by evaporating three neutrons as compared with their neigbouring even-A compound nuclei.
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Polarization Patterns Control Based on Photoinduced Anisotropy of Photochromic Fulgide
WANG Ying-Li, YAO Bao-Li, MENKE Neimule, CHEN Yi, LI Tian-Kai, ZHENG Yuan, LEI Ming, DONG Wei-Bin, FAN Mei-Gong, CHEN Guo-Fu
Chin. Phys. Lett. 2004, 21 (4):
679-681
.
We investigate the photoinduced anisotropy of a photochromic material of pyrrylfulgide/PMMA films. It is proven that when the film is illuminated with a linear polarization light, an optical axis that has the same polarization as the excitation light could be induced in the film. A matrix of light spots with different polarizations is recorded on the pyrrylfulgide/PMMA film. When reading out with non-polarization light, the matrix of light spots shows no information of patterns. However, when reading out with different linear polarization lights, different patterns could be observed. The experiment confirms that the pyrrylfulgide/PMMA film could be used to record two different polarization patterns in a matrix of spots. This property may be applied in camouflage technology.
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Stabilization of Viscosity on Rayleigh-Taylor Instability in Z Pinches
QIU Xiao-Ming, HUANG Lin, JIAN Guang-De
Chin. Phys. Lett. 2004, 21 (4):
689-692
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On the basis of incompressible viscid magnetohydrodynamic equations, a formula is developed to study the mitigation of viscosity on the Rayleigh-Taylor instability in Z pinches. The results indicate that in the whole wavenumber region, the viscosity effect can mitigate the instability. In addition, we compare the viscosity effect with the finite Larmor radius effect [Chin. Phys. Lett. 19 (2002) 217], and the calculation results show that in the temperature region of interest, the former is stronger than the latter. Moreover, for heavy wire-array implosion the viscosity effect is stronger than the finite Larmor radius one, because the former is proportional to m1/2i and the latter is independent of mi.
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Double Jet Emission of Hot Electrons from a Micro-droplet Spray
PENG Xiao-Yu, ZHANG Jie, LIANG Tian-Jiao, SHENG Zheng-Ming, JIN Zhan, LI Yu-Tong, WANG Zhao-Hua, YU Quan-Zhi, ZHENG Zhi-Yuan, LIU Yun-Quan, WU Hui-Chun, HAO Zuo-Qiang, YUAN Xiao-Hui, WEI Zhi-Yi
Chin. Phys. Lett. 2004, 21 (4):
693-696
.
Spatial distribution of hot electrons with energies above 50 keV are investigated by an ethanol micro-droplet spray irradiated by linearly and elliptically polarized 150 fs laser pulses at an intensity of 1016W/cm2. Two symmetric hot electron jets with respect to the laser propagation direction are observed in the polarization plane for a linearly polarized laser field and in the plane of the long electric vector for an elliptically polarized laser field, respectively. Particle-in-cell simulations suggest that the resonance absorption on the spherical surface of the droplets is mainly responsible for the generation of the double-jet emission of hot electrons.
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A New Model for Microstructure of Liquid Metals
TIAN Xue-Lei, SHEN Jun, SUN Jian-Fei, Li Qing-Chun
Chin. Phys. Lett. 2004, 21 (4):
700-703
.
A nanocrystalline model for microstructures of liquid metals is constructed. According to the nanocrystalline model, the intensity curves of x-ray diffraction (XRD) on liquid Cu, Al and Al65Cu20Fe15 alloy are derived by broadening the XRD peaks of these metals in some crystal structures. These broadening intensity curves are identical with the results measured by an x-ray diffractometer on these liquid metals. The present results indicate that the nanocrystal model may be helpful to understand the microstructures of liquid metals and that there is a close correlation between the short-range orders (SROs) of these liquid metals and some crystal lattice structures. That is, the SRO structures of liquid Cu, Al and Al65Cu20Fe15 alloy are fcc, bcc and icosahedron, respectively.
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Effects of Er2O3 on Electrical Properties of the SnO2.CoO.Ta2O5 Varistor System
WANG Chun-Ming, WANG Jin-Feng, CHEN Hong-Cun, SU Wen-Bin, ZANG Guo-Zhong, QI Peng
Chin. Phys. Lett. 2004, 21 (4):
716-719
.
We investigate the effects of Er2O3 on electrical properties of the SnO2.CoO.Ta2O5 varistor system sintered at 1400°C. It is found that all the samples have excellent nonlinear electrical characteristics and the sample with 0.50 mol% Er2O3 has the best nonlinear electrical property and the highest nonlinear coefficient (α = 43.7). The high nonlinear coefficient value obtained in the system indicates that the SnO2-based varistor is a candidate for ZnO-based varistors in commercial applications. Er2O3 additive can significantly affect the average grain size. With increasing Er2O3 concentration from 0.10 mol% to 1.00 mol%, the average grain size decreases from 21.2μm to 10.6μm, the breakdown electrical field increases from 208 V/mm to 459 V/mm, and the relative electrical permittivity decreases from 2440 to 1210. The reason that the grain size decreases with increasing Er2O3 concentration is explained. Also, we present a modified defect barrier model to illustrate the grain-boundary barrier formation of Er2O3-doped SnO2 based varistors.
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Influence of Polarization Effects on the Energy Band of AlGaN/GaN/AlGaN Heterostructures
WEN Bo, JIANG Ruo-Lian, ZHOU Jian-Jun, JI Xiao-Li, LIANG Ling-Yan, KONG Yue-Chan, SHEN Bo, ZHANG Rong, ZHENG You-Dou
Chin. Phys. Lett. 2004, 21 (4):
720-722
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The unintentionally doped samples of Al0.22Ga0.78N/GaN/Al0.22Ga0.78N/GaN multi-heterostructures have been designed and fabricated. The polarization induced charge and free-carrier charge distributions have been demonstrated and the energy band profile has also been calculated. The results indicate the existence of two-dimensional electron gas (2DEG) and hole well at the heterointerfaces. By means of variable temperature Hall measurements, the carrier mobility and the sheet carrier density were measured from 300 to 77 K. The significant increment of carrier mobility at low temperature also verified the existence of the 2DEG.
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Surface Spins Pinning Effect on the Magnetic Properties in Co3O4 Nanocrystallites Covered with Polymer Decomposition Residues
LI Shan-Dong, BI Hong, FANG Jiang-Lin, ZHONG Wei, DU You-Wei
Chin. Phys. Lett. 2004, 21 (4):
737-740
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We prepare two kinds of Co3O4 antiferromagnetic nanocrystallite systems with different surface structures: one grain surface is covered by polymer decomposition residues (PDRs) (referred to as CS) and the other is naked (NS). It has been found that the magnetic properties of the CS sample deviate greatly from those of the NS sample. For example, the CS sample exhibits an open loop up to 8 T at 4.2 K, while the two branches of the hysteresis loop for the NS sample superpose together when the field is in excess of 3 T. The average permanent magnetic moments per Co3O4 cell for the CS sample are about three times larger than that of the NS sample. The coercivity and loop shift for the CS sample are enhanced remarkably in comparison with the NS sample, i.e., from 73.8 and 11.0 kA/m for the NS sample to 116.5 and 25.5 kA/m for the CS sample, respectively. The anomalous magnetic properties and their enhancements for the CS sample are attributed to the surface spin pinning effect by PDRs.
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Supercontinuum Generation with 15-fs Pump Pulses in a Microstructured Fibre with Random Cladding and Core Distributions
ZHENG Yi, ZHANG Yu-Ping, HUANG Xiao-Jun, WANG Li, WANG Yan-Yong, ZHOU Kai-Nan, WANG Xiao-Dong, GUO Yi, YUAN Xiao-Feng, ZHOU Gui-Yao, HOU Lan-Tian, HOU Zhi-Yun, XING Guang-Zhong, YAO Jian-Quan,
Chin. Phys. Lett. 2004, 21 (4):
750-753
.
A supercontinuum extending from 350 nm to more than 1700 nm is generated in microstructured fibre (MF) with randomly distributed air holes in cladding and core by using 15-fs pulses of a 790-nm laser. The maximum total power of the supercontinuum is 63 mW with 288 mW pump power from a 100 x microscope objective. The wavelength and power of visible light ranging in the supercontinuum can be tuned by adjusting the input end of random the MF (to change pump incident point or incident angle). In particular, white light has been observed. The polarization states and waveguide modes of the visible light change with adjustment of the pump incident point or incident angle.
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Electromagnetic Quantities in Black Hole Magnetosphere
WANG Ding-Xiong, MA Ren-Yi, LEI Wei-Hua, YAO Guo-Zheng
Chin. Phys. Lett. 2004, 21 (4):
766-766
.
Some electromagnetic quantities in the black hole (BH) magnetosphere are discussed by considering the coexistence of the Blandford-Znajek process and the magnetic coupling process. These quantities are (i) flux of electromagnetic energy and angular momentum transferred between the BH and the disc, (ii) poloidal currents flowing on the horizon and disc, (iii) poloidal electric field on the horizon, (iv) toroidal magnetic field in the BH magnetosphere, and (v) voltage drop across the magnetic coupling region on the horizon. It turns out that these quantities are determined mainly by three parameters: (i) the positions relative to the corotation magnetic surface, (ii) the BH spin, and (iii) the power-law index for the variation of the magnetic field on the disc.
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50 articles
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