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Chin. Phys. B  
  Chin. Phys. B--1997, Vol.6, No.1
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GENERAL

SOLVABLE BOSON-FERMION MODEL FOR MIXED-VALENCE SYSTEMS

MA XUAN-RONG, LIU WU-MING, ZHAO HONG-WEI, PU FU-CHO
Chin. Phys. B 1997, 6 (1): 01;  doi: 10.1088/1004-423X/6/1/001
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Using the Bethe ansatz technique, the exact eigenstates of the Hamiltonian of the boson-fermion model for mixed-valence systems are constructed. The Bethe ansatz equations are obtained from the periodic boundary conditions.
ATOMIC AND MOLECULAR PHYSICS

THE MULTIPLE IONIZATION OF ARGON INDUCED BY PARTIALLY STRIPPED CARBON IONS

CAI XIAO-HONG, SHEN ZI-YONG, CHEN XI-MENG, LIU ZHAO-YUAN, MA XIN-WEN, LIU HUI-PING, HOU MING-DONG
Chin. Phys. B 1997, 6 (1): 06;  doi: 10.1088/1004-423X/6/1/002
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The cross section ratios of the double, triple and quadruplicate ionization to the single ionization of argon by 1.5-7.5 MeV partially stripped carbon ions are measured by using time-of-flight technique. The Auger transition and the charge exchange process in the multiple ionization of argon are studied. The ratios of cross sections of the direct multiple ionization to those of the direct single ionization are obtained by subtracting the parts of the Auger transition and the charge exchange process from the measured data. It is found that the cross section ratios of the direct multiple ionization to those of the direct single ionization are in good agreement with the predicted mniti-step (ν/qeff)-2n+2 law.
CLASSICAL AREAS OF PHENOMENOLOGY

ELECTROMAGNETICALLY INDUCED FOCUSING IN A Λ-TYPE MEDIUM

GONG SHANG-QING, XU ZHI-ZHAN
Chin. Phys. B 1997, 6 (1): 013;  doi: 10.1088/1004-423X/6/1/003
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Electromagnetlcally induced transparency (EIT) in an inhomogenously broadened medium consisting of Λ-type three-level atoms has been analyzed. It is shown that the A system can induce a transparency of the medhun when the probe laser and the coupling laser have the same frequency detunings (including zero). Across the EIT window, the radial variation of the strong coupling laser radiation may lead to electromagnetically induced focusing or defocusing of the weak probe laser at separate probe frequency detuning points.

GENERATION OF MULTI-WAVELENGTH VISIBLE LIGHT IN Er3+-DOPED AND Er3+/Yb3+-DOPED SINGLE-MODE OPTICAL FIBER PUMPED AT 1313 nm

HU WEI, LIU DONG-FENG, CHEN GUO-FU, WANG XIAN-HUA, HOU XUN
Chin. Phys. B 1997, 6 (1): 018;  doi: 10.1088/1004-423X/6/1/004
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We report the generation of multi-wavelength visible light through amplified spontaneous emission (ASE) in Er3+-doped and Er3+/Yb3+-doped germanosilicate single-mode optical fiber pumped by a Nd:YLF laser at 1313nm. In the Er3+-doped fiber, the intense multi-wavelength blue emission hnes around 463-510nm corre-spond to transitions born 2G7/2 etc. excited states to the metastable 4I13/2 state, and their pumping mechanists is aecomphshed by a stepwise four-photon absorption. Some emission hnes in this wavelength region are attributed to the three-wave sum-frequency process of 1313 and 1530nm (corresponds to 4I13/2 -4I15/2). The intense green emission hnes at 525 and 540 nm are also observed in the Er3+-doped fiber. In the Er3+/Yb3+-doped fiber the blue and green lines are very weak compared with those in the Er3+-doped fiber.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

POWDER NEUTRON DIFFRACTION STUDIES OF THE CRYSTALLOGRAPHIC AND MAGNETIC STRUCTURE OF Ho2Fe9Ga8 and Ho2Fe9Ga6AI2

CHENG DONG-FENG, GOU CHENG
Chin. Phys. B 1997, 6 (1): 024;  doi: 10.1088/1004-423X/6/1/005
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The crystallographic and magnetic structures of Ho2Fe9Ga8 and Ho2Fe9Ga6AI2 were studied by powder neutron diffraction at room temperature. The atom fractional occupancies of Ga and Al and the magnetic moments of Ho and Fe were obtained by using Rietveld analysis program. The magnetic structures of the two samples show an easy-axis anisotropy, with the Fe magnetic moment being ferrimagneticlly coupled to those of Ho.

STUDY ON THE CATHODE DEPOSIT PRODUCED IN THE PROCESS OF CARBON ARC DISCHARGE

LI FAN-QING, LU BIN, ZUO JIAN, CHEN ZHI-WEN, JIA YUN-BO, LU JIANG, ZHANG SHU-YUAN, ZHOU GUI-EN
Chin. Phys. B 1997, 6 (1): 028;  doi: 10.1088/1004-423X/6/1/006
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The cathode deposit produced by carbon are discharge wae studied by scanning electron microscopy, high resolution electroa microscopy, X-ray diffraction and Raman spectroscopy. The results indicate that the stacking of hexagonal carbon layer in the discharged graphite is different from the ABAB stacking sequence in graphite, and that carboy nanotube is a kind of graphite-like micro-crystal with a low-dimensional structure.

PHASE TRANSITION IN A NONEQUILIBRIUM POTTS MODEL WITH COMPETING DYNAMICS: A MONTE-CARLO STUDY

GUO WEN-AN, YANG ZHAN-RU
Chin. Phys. B 1997, 6 (1): 035;  doi: 10.1088/1004-423X/6/1/007
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The nonequilibrium steady state of three-state Potts model evolving under combined Glauber dynamics at temperature β-1 and Kawasaki dynamics at β′= 0 is studied by Monte-Carlo simulations. As the exchange rate p increases, the phase transition changes from second to first order. The critical exponents of second-order transition are independent of p, and the critical properties for different p belong to the same universality class.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

ELECTRONIC STRUCTURE OF Hg0.8Pb0.2Ba2Ca2Cu3O8+δ: THE ROLE OF Pb DOPING, OXYGEN DOPING AND HIGH PRESSURE

Lü JING, ZHANG LI-YUAN, HAO XUE-JUN
Chin. Phys. B 1997, 6 (1): 040;  doi: 10.1088/1004-423X/6/1/008
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The effects of Pb doping, oxygen doping (δ= 0.1,0.2,0.4 and 0.5) and high pressate (4, 8, 15 and 20GPa) on the electronic structure of Hg0.8Pb0.2Ba2Ca2Cu3O8+δ have been examined by the recursion method. Our calculations show that Pb doping only decreases the hole concentration slightly and oxygen doping increases the hole concentration monotonically and significantly as δ varies from 0 to 0.5, with each excess oxygen atom contributing about 1.7 holes to the CuO2 layers. The optimal δ is estimated to be around 0.4, The hole conceatration increases initially with pres-sure but decreases as P > 8GPa (i.e., dn/dP does change sign at ~ 8GPa). The suppressed Tc(P) by Pb substitution has to be described in the modified Neumeier's model.

STRUCTURE AND PHOTOELECTRIC PROPERTIES OF HYDROGENATED AMORPHOUS SILICON-GERMAN-IUM ALLOYS PRODUCED BY HIGH HYDROGEN DILUTION METHOD

XU JUN, CHEN KUN-JI, FENG DUAN, MIYAZAKI SEIICHI, HIROSE MASATAKA
Chin. Phys. B 1997, 6 (1): 052;  doi: 10.1088/1004-423X/6/1/009
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A series of hydrogenated amorphous silicon-germanium alloys have been fabricated by high hydrogen dilution method. The Ge content in the film increasea from 0.4 to 0.8 and the corresponding optical bandgap is in the range of 1.48-1.22eV. The photoconductivity is 3.6×10-6 S/cm and photosensitivity is as high as 7.3×103 at an optical bandgap of 1.48eV. The deterioration of photoelectric properties with increasing Ge content could be attributed to the decrease of the bonded hydrogen content and the inhomogeneous structure in the alloy network.

ELECTRON SPIN RESONANCE CHARACTERISTICS OF NITROGEN-DOPED FULLERENE

CHEN GUANG-HUA, XIE ER-QING, ZHANG XING-WANG
Chin. Phys. B 1997, 6 (1): 057;  doi: 10.1088/1004-423X/6/1/010
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The nitrogen-doped fullerene has been obtained by arc discharge between two high-purity graphite rods in the atmosphere of N2 and He, The electron spin resonance(ESR) characteristics of N-doped fullerene have been investigated. The results show that the ESR spectra of N-doped fallerene axe composed of two parts, a paramagnetic signal of N-center and a paramagnetic signal of C-center, For comparing with N-doped fullerene, we have also studied ESR spectra of C60 powder, C60 sublimed film and H-doped C60 film. For C60 powder and H-doped C60 film, their in situ ESR. measurements are carried out at various temperatures, and reasonable explanations are proposed.

A STUDY OF RAMAN SCATTERING AND INFRARED ABSORPTION SPECTRUM IN A NEW SERIES OF MERCURY-BASED HIGH-Tc SUPERCONDUCTOR (Hg,Mo)Sr2(Y1-xCax)Cu2O6+δ

XU CUN-YI, TANG KAI-BIN, ZUO JIAN, XU XIAO-WEN, ZHU JING-SHENG, QIAN YI-TAI, ZHANG YU-HENG
Chin. Phys. B 1997, 6 (1): 065;  doi: 10.1088/1004-423X/6/1/011
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Lattice vibrations of the (Hg,Mo)Sr2(Y1-xCax)Cu2O6+δ—a new series of mercury-based high-Tc superconductor are analyzed with the aid ofgroup theory. The vibrations of species are given. They are 4A1g+ B1g+ 5Eg+ 7A2u + B2u+ 8Eu. The 4A1g, B1g and 5Eg modes are Ramma active, the 6A2u and 7Eu are infrared active. Phonon vibration characteristics of the samples are studied using Raman scattering and infrared absorption spectra. The experimental results show that the typical phonon vibrational modes appear mainly at 145, 320, 440, 578, 592 and 645cm-1, The intensities of the 145, 320, 440, 578 and 645 peaks decrease with increasing Ca content x and the position of 645 peak moves to higher wavenumber slightly. In this article, the phonan modes are assigned and their variation behavior with increasing Ca content x are discussed.
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