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Nuclear Radii Extracted from Experimental Reaction Cross Sections
ZHANG Hu-Yong, SHEN Wen-Qing, REN Zhong-Zhou, MA Yu-Gang, JIANG Wei-Zhou, CAI Xiang-Zhou, ZHONG Chen, CHEN Jin-Gen, GUO Wei, WEI Yi-Bin, ZHOU Xing-Fei, MA Guo-Liang, WANG Kun
Chin. Phys. Lett. 2003, 20 (8):
1234-1237
.
We illustrate typical experimental reaction cross sections σR which have obtained on RIBLL at Heavy Ion Research Facility of the Institute of Modern Physics (IMP) at Lanzhou. The corresponding nuclear radii are extracted from the measured experimental σR using the Glauber model. Meanwhile, theoretical nuclear radii are also calculated using Relativistic density-dependent Hartree and spherical relativistic mean-field theory with Pauli blocking. For comparison, the nuclear radii of these nuclei are also calculated using the empirical radius format in which the deformation has been taken into account. From the given experimental and theoretical nuclear radii, we suggest that there may exist proton halo structure in 23Al, 27P and may exist proton skin structure in 24Al. We also find that the deformation plays a great role to the nuclear radii.
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Theoretical Analysis of Ionic Autoionization Spectra of Lanthanum in the Energy Region of 90650-91500 cm-1
ZHANG Xin-Feng, PENG Yong-Lun, ZHONG Zhi-Ping, QU Yi-Zhi, SUN Wei, XIA Dan, XUE Ping, XU Xiang-Yuan,
Chin. Phys. Lett. 2003, 20 (8):
1242-1243
.
Eigenquantum defects μα and transformation matrix Uiα of La+ are calculated from the first principles by relativistic multichannel theory, and dipole matrix elements Dα are obtained by fitting the experimental spectra. With these parameters, ionic autoionization spectra of lanthanum via an intermediate state (Xe)5d6d1P1 of La+ in the energy region of 90650-91500cm-1 are calculated within the framework of multichannel quantum defect theory. Our calculated spectra are in general agreement with the experimental data.
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Optimal Truncation in Ionization of Hydrogen by Electron Impact
ZHANG Cheng-Hua, NIU Ying-Yu, WU Wei, QIU Wei, XIN Jun-Li, WANG Xiao-Wei, WANG Jing-Yang
Chin. Phys. Lett. 2003, 20 (8):
1244-1246
.
An analytic expression for the ionization amplitude of hydrogen by electron impact is found to contain a polynomial by an optimal truncation in an asymptotic series and a convergent series. The ionization amplitude, i.e., transition matrix element on the energy shell, is decomposed into two parts: the structure-scattering factor and correlation factor, based on an approximation of projectile plane wave in coplanar asymmetric geometries. The contribution of these factors to the triple differential cross section is evaluated using the method of optional truncation of asymptotic and convergent series.
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Generation of Very Energetic Ions from Intense Femtosecond
Laser Interactions with Rare Gas Clusters in a Dense Jet
LI Shao-Hui, WANG Cheng, ZHU Pin-Pin, WANG Xiang-Xin, LI Ru-Xin, NI Guo-Quan, XU Zhi-Zhan
Chin. Phys. Lett. 2003, 20 (8):
1247-1250
.
Very energetic ions, which are detected by time-of-flight spectrometry with the maximum energy up to 1.3 MeV and an average energy of 68 keV, are generated in the explosion of large Xe clusters in a dense jet irradiated with a high intensity (~1016W/cm2) 50 fs laser pulse from a Ti:sapphire TW laser at 790 nm wavelength. The interaction of intense laser pulses with a jet of argon clusters is also performed and high average ion energies are observed. The dependence of energy of the ions on gas backing pressure is examined, suggesting that the results are consistent with the absorption efficiency of the laser energy by the cluster plasmas.
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Investigation of Electron Injection Parameters in Vacuum Laser Acceleration
SHAO Lei, HUO Yu-Kun, CAO Na, PANG Ju, CHEN Zhao, XIE Yong-Jie, ZHANG Shao-Yin
Chin. Phys. Lett. 2003, 20 (8):
1251-1253
.
We investigate the parameters such as the energy gains, comparisons for linearly and circularly polarized laser fields, the electron incident polarization azimuth angle, the electron incident crossing angle, and the electron incident momentum, etc., which are crucial for experimental test of the vacuum laser acceleration scheme in capture and acceleration scenario (CAS) [see, e.g., Phys. Rev. E 66 (2002) 066501]. Physical explanation of these features has been presented based on the CAS scheme. The results show that all those parameters are in the reasonable ranges obtainable by presently experimental facilities.
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Vertical and Smooth, etching of InP by Cl2/CH4/Ar Inductively Coupled Plasma at Room Temperature
SUN Chang-Zheng, ZHOU Jin-Bo, XIONG Bing, WANG Jian, LUO Yi
Chin. Phys. Lett. 2003, 20 (8):
1312-1314
.
We study the room-temperature dry etching of InP by inductively coupled plasma (ICP) using Cl2/CH4/Ar mixtures. Etches were characterized in terms of anisotropy and surface roughness by scanning electron microscopy and atomic force microscopy, respectively. It is found that the flow ratio between Cl2 and CH4, ICP power, rf chuck power, and table temperature can greatly influence the etching results. By adjusting etching parameters, vertical sidewall and smooth surface can be obtained simultaneously, together with a moderate etch rate and a good select ratio. The root-mean-square surface roughness is measured to be as low as 0.27 nm. To our knowledge, this is the best result for InP to date. The etch rate is 855 nm/min, and the selectivity ratio over SiO2 is estimated to be higher than 15:1. The stoichiometry of the etched surface has also been investigated by Auger electron spectroscopy. The etched surface is found to manifest a slight P deficiency, and the ratio between P and In reaches the stoichiometric value within about 0.75 nm depth into the surface.
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Aligned ZnO Nanofibre Array Prepared by Vapor Transport in Air
XU Chun-Xiang, SUN Xiao-Wei, CHEN Bai-Jun, SUN Chang-Qing, TAY Beng-Kang, LI Sui-Xiang Sean
Chin. Phys. Lett. 2003, 20 (8):
1319-1322
.
An aligned zinc oxide nanofibre array has been fabricated by heating the mixture of ZnO, Ga2O3, and graphite powders in atmosphere. The ZnO nanofibre showed a uniform size of about 150 nm in diameter and 50μm in length. The nanofibres grew predominantly along one direction. Both x-ray diffraction (XRD) and Raman shift spectra show that the product is composed of ZnO with the typical hexagonal structure. The good crystallinity of these ZnO nanofibres has been verified by photoluminescence spectra with strong UV emission at 287 nm and weak green band emission observed at room temperature. The component of the product was analysed by XRD, Raman shift spectrum, x-ray energy dispersion (EDX) and x-ray photoelectronic energy spectroscopy (XPS). The growth process and the characteristics can be interpreted by vapor-liquid-solid mechanism.
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Low Resistivity C54 Phase TiSi2 Films Synthesized by a Novel Two-Step Method
LI Dan-Feng, GU Chang-Zhi, GUO Cai-Xin, YUE Shuang-Lin, HU Chang-Wen,
Chin. Phys. Lett. 2003, 20 (8):
1329-1332
.
Synthesis and growth properties of the TiSi2 film on a Si (001) substrate are investigated. A novel two-step method is used for deposition of the C54 phase TiSi2 film with low resistivity. The first step is the formation of the C49 phase TiSi2 at a relative low substrate temperature of 400°C, followed by rapid thermal annealing process at 850°C in N2 for the formation of the C54 phase TiSi2 as the second step. Finally, selective wet etching is employed to remove the un-reaction Ti on the surface and the low resistivity C54 TiSi2 film can be obtained. The films deposited under various parameters are evaluated by scanning electron microscopy, x-ray diffraction and the resistivity measurement. Compared with other sputtering technologies used commonly for TiSi2 synthesis, this two-step method has apparent advantages such as the mild synthesis temperature and the high purity of the final product with low resistivity, uniform large area and improving surface roughness. In addition, the film also shows that the low coefficient of resistivity-temperature appears in the temperature range from 20°C to 800°C.
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High Efficiency Infrared to Visible Upconversion in Er3+/Yb3+-Doped Lead Halide Tellurite Glass
ZHANG Li-Yan, YANG Jian-Hu, HU Li-Li, JIANG Zhong-Hong
Chin. Phys. Lett. 2003, 20 (8):
1344-1346
.
Strong upconversion luminescence of Er3+/Yb3+-doped lead halide tellurite glass under 976 nm excitation is demonstrated. Three emission bands centered at 525 nm, 545 nm, and 655 nm resulting from the transitions from the excited states 2H11/2, 4S3/2, and 4F9/2 to the ground state 4I15/2, respectively, are observed even at 60 mW pumping power. The power dependent intensity and the upconversion mechanisms responsible for the luminescences are evaluated and discussed. The obtained results might provide useful information for the developments of upconversion lasers.
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Thermal Annealing of SiO2 Fabricated by Flame Hydrolysis Deposition
ZHANG Le-Tian, XIE Wen-Fa, WU Yuan-Da, XING Hua, LI Ai-Wu, ZHENG Wei, ZHANG Yu-Shu
Chin. Phys. Lett. 2003, 20 (8):
1366-1368
.
Amorphous SiO2 films were fabricated on Si substrates by flame hydrolysis deposition as buffer layers applied in the planar optical waveguides. Then the Si wafers with the porous particles were put into electric furnace annealing at different temperatures for consolidation in air. The products were characterized by x-ray diffraction, x-ray
photoelectron spectroscopy, atomic force microscopy, and variable angle spectroscopic ellipsometry. It was found that different structures at different annealing temperatures were obtained. When the annealing temperature arrives at 1400°C, SiO2 is continuous and dense and the refractive index at 1550 nm is 1.4564, which is highly desirable.
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Surface Plasmon-Assisted Excitation of Atomic Visible Light Spectral Lines in the Impact of Highly Charged Ions 126Xeq+ on Solid Surfaces
ZHANG Xiao-An, ZHAO Yong-Tao, LI Fu-Li, YANG Zhi-Hu, XIAO Guo-Qing, ZHAN Wen-Long
Chin. Phys. Lett. 2003, 20 (8):
1372-1375
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We measured the visible light spectral lines of sputtering atoms from solid surfaces of Al, Ti, Ni, Ta and Au which are impacted by 150 keV 126Xeq+ (6 ≤ q ≤ 30). It is found that intensities of the light spectral lines are greatly and suddenly enhanced when the charge state of the ion is raised up to a critical value. If assuming that potential energy released from the incident ion due to capturing one electron is enough to excite a surface plasmon, we can estimate the critical charge states and obtain the results very well consistent with the measurements for the above mentioned target materials. This means that a surface plasmon induced by one electron capture can enhance the excitation of atomic visible light spectral lines in the impact of a highly charged ion on a solid surface.
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Structural Properties of US Flight Network
CHI Li-Ping, WANG Ru, SU Hang, XU Xin-Ping, ZHAO Jin-Song, LI Wei, CAI Xu
Chin. Phys. Lett. 2003, 20 (8):
1393-1396
.
We analyse the directed, weighted and evolutionary US flight network, in which vertices are the airports and the flights connecting two airports represent the edges. It is shown that such a network displays two important features recently found in small-world networks. First, the average shortest-path length is 2.4 s, the clustering coefficient of the entire network, 0.618, is greatly larger than that of the random networks with the same N (system size) and (average degree), 0.065. We study the detailed flight information both in a week and on a whole. In both the cases, using the Pareto distributions, we find the degree distributions follow two-segment power laws. The weight distributions have power-law tails with the exponents of around 2, and the clustering coefficient distributions follow linear distributions.
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66 articles
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