Synthesis of C26 Crystallite Polyethylene by C2+ Ion Bombardment

A new form solid Carbon has been synthesized consisting of a hexagonal close packing of a26 molecules under energetic C₂₆ ion 2.4 MeV bombardment of ultra high molecular weight polyethylene. The beam current was about 150 mA and the total dose was 1×10¹⁶ ions cm^－2. The residual gas pressure in the irradiation chamber was 1.3×10^－4Pa during bombardment High-resolu-tion transmission electron microscopy, electron diffraction, and time-of-flight mass spectroscopy studies of the molecular packing confirm that the C₂₆ molecules have the Caged fullerene structure.     

Dielectronic Recombination of Sn^10＋ Ions and Related Satellite Spectra

Based on the multi-configuration Dirac-Fock method, theoretical calculations are carried out for the dielectronic recombination （DR） rate coefficients and the collision excitation rate coefficients of Sn^10＋ ions. It is found that the total DR rate coefficient has its maximum value between 10eV and 100eV and is greater than either the radiative recombination or three-body recombination rate coefficients （the number of free electrons per unit is 10^21 cm^3） for the ease of Te 〉 1 eV. Therefore, DR can strongly influence the ionization balance of laser produced multi-charged tin ions. The related dieleetronie satellite cannot be ignored at low temperature Te 〈 5 eV.     

高温高压合成CeTbO3+δ的XPS研究

 经过高温高压合成的CeTbO_3+δ进行了XPS研究，发现在1.0 GPa下，Tb⁴⁺在~600 ℃开始转变成Tb³⁺，而Ce⁴⁺在~800 ℃开始向Ce³⁺转变。在1 000~1 200 ℃形成单相萤石结构化合物CeTbO_3+δ的Ce是以Ce³⁺、Ce⁴⁺混合价形式存在，Tb全部变成Tb³⁺。实验表明，用Ce_3d谱上~888 eV峰的峰位及其与882 eV峰的相对强度变化可以定性判断化合物中是否含有Ce³⁺。研究了高温高压合成的CeTbO_3+δ的稳定性随时间的变化问题。     

金属性氧化物LaCuO3的高氧压合成及Cu3+态的XPS研究

 本文在成功地用超高氧压（~6.5 GPa）及高温（~980 ℃）合成和结构测定的基础上，首次对金属性化合物中LaCuO₃中的Cu³⁺离子给予标定，并研究了它与绝缘体中Cu³⁺的区别。本论文中合成的LaCuO₃为金属性化合物，电导率测量表明在大于13 K无超导电性迹象。XPS测量给出了LaCuO₃中Cu2p_3/2内层电子结合能相对于La₂CuO₄或CuO中的Cu²⁺向高结合能方向移动了约2.6 eV，这一量值远大于NaCuO₂（绝缘体）中的Cu2p_3/2相对于CuO中的Cu²⁺移动的值，约为1.3 eV。Auger谱测量表明，LaCuO₃的修正了的Auger参数与CuO的基本相同，但L₃VV的Auger电子动能相对CuO移动了2.8 eV。这些位移说明在金属性化合物LaCuO₃中，Cu³⁺处在八面体位置上，它与近邻的Cu³⁺连成单个Cu—O—Cu桥，因此可作为对比p型高T_c含铜氧化物的XPS谱的标准。     

Electron Scattering by C4H10 and C6H6 in the Energy Range 100--1000eV

We investigate the applicability of the independent atom model （IAM） to elastic electron scattering from complex polyatomic molecules, namely C4H10 and C6H6, in the energy range 100-1000eV. The cross sections of the elastic electron scattering are calculated by employing the IAM together with the relativistic partial waves. The incorporation of both the modified absorption potential and the extended structural factor in the IAM makes the elastic differential cross sections and momentum transfer cross sections have a good agreement with the available experimental data. The present simple model seems to be insensitive to the complexity of the target molecules so that the proposed procedure can be quite useful for calculation of electron scattering from bio-molecules.     

Effect of heat treatment on UV-laser-induced positive ion desorption in CaHPO4·2H2O

We have investigated KrF excimer-laser-induced positive ion desorption from single-crystal brushite (CaHPO₄·2H₂O), a model biomineral containing water, and we show the effect of heat treatment on ion desorption. Time-of-flight peaks of Ca⁺ desorption from the heated-cleaved surface are similar to those from as-cleaved ones, but the ion intensity is 2 to 4 orders of magnitude larger. In addition to Ca⁺, desorption of CaO⁺, PO⁺, and P⁺ from the heated surface is also strongly enhanced. The heated-cleaved surface shows rough, platelet-like fine structures due to recrystallization. Surface defects created during recrystallization strongly couple with the 5 eV photons and dramatically enhance ion desorption.     

立方氮化硼的振动光谱及反射光谱的研究

 将黑色、黄色、棕色三种小于50 μm立方氮化硼粉末为样品，研究了其红外光谱、拉曼光谱、反射光谱，结果表明：（1）样品的红外光谱中，1 818 cm^-1和1 548 cm^-1属于cBN的晶格本征振动，而立方氮化硼的晶格本征振动外的晶体缺陷吸收则发生在~800 cm^-1，1 580 cm^-1~1 740 cm^-1和大于2 400 cm^-1处。（2）拉曼光谱测试表明，在1 052 cm^-1和1 304 cm^-1附近出现的散射与cBN不具有反演中心及cBN具有立方结构这样的事实相一致，并且这种散射伴随着布里渊区中心声子的横向和纵向发射。144 cm^-1附近出现的散射，被认为是由于局部振荡模式的出现，在反斯托克斯区造成的信号，这与晶格中杂质缺陷有关。（3）依据得到的反射光谱，计算了cBN单晶禁带宽度，发现这三种cBN都具有大于金刚石的禁带宽度值，分别为：E_g(黑)=6.21 eV，E_g(黄)=5.73 eV，E_g(棕)=5.71 eV。     

The Observation of Positron Surface State of Germanium

The formation yield of positronium (Ps) as a function of target temperature has been measured when positron implanting energy was 20eV.By thermal dynamic analyising we obtained the binding energy E_b of positron surface state of germanium to be 2.2eV and the thermal activation energy E_a of Ps to be 0.2±0.01eV at vacuum 1.33×10^－4Pa.The different of E_b and E_a at the condition of high and ultra-high vacuum was discussed.     

Ruthenium oxide and strontium ruthenate electrodes for ferroelectric thin-films capacitors

Metallic ruthenium and ruthenium oxides, such as SrRuO₃ and RuO₂, are potential electrode materials for ferroelectric capacitors. The electrical properties (e.g. leakage currents) of such thin film devices are dependent on the electronic properties of the electrode/ferroelectric junctions and therefore also on the electrode work functions. During growth and processing of film-electrode layer structures the formation of sub-oxides within the electrode is possible, with their work functions being unknown. In order to obtain information for predicting device properties, we have systematically analysed the valence bands and work functions of RuO_x and SrRuO_y thin films with different oxidation states by using photoelectron spectroscopy techniques. The results suggest that Ru⁰ and Ru⁴⁺ ions are present in co-existence at the surfaces of oxygen-deficient polycrystalline films (inhomogeneous oxidation). For both oxygen-deficient materials the work function coincides with that of metallic ruthenium (4.6ǂ.1 eV). Only for fully oxidised ruthenium oxide and strontium ruthenate films (no Ru⁰ present at the surface) is the work function increased to 5.0 or 4.9 eV, respectively. As an example of importance for new dynamic random access memory applications, the junctions of Ba_1-xSr_xTiO₃ with SrRuO_y and RuO_x are discussed.     

VUV/UV/X-Ray Excited Luminescent Properties of Eu^3＋ and Pr^3＋ Doped BiSbO4

Absorption spectra of BiSbO4 are studied. The electronic structure calculated by the DFT shows that BiSbO4 is a semiconductor, with direct band gap 2.96 eV, which is consistent with UV-visible diffuse reflectance experiment. The host lattice emission band is located at 440 nm under VUV excitation. Eu^3＋ and Pr^3＋ doped samples have high luminescence efficiency in emitting red and green light, respectively. From the partial density of states, Eu^3＋ doped emitting spectrum, and the host crystal structure parameters, the relationship between structure and optical properties is discussed. It is found that the Eu^3＋ ions occupied Bi^3＋ sites, and there could be an energy transfer from Bi^3＋ ions to RE^3＋ ions.     

THE RIGHT-HANDED CURRENTS OF NEUTRINOLESS DOUBLE β DECAY IN 48Ca

Right-handed Currents in 0νββ decay with lepton-number nonconservation is discussed by using two nucleons mechanism and the effective operator approach of nuclear matrix elements in this paper. The relation between the mixing parameter η of right-handed currents and the Majorana neutrino mass m_ν is calculated from the experimental decay lifetime of 0νββ decay in ⁴⁰Ca. Our results show that i) m_ν≤(18~23)eV, if |η|=0;ii) |η|≤(1.6~2)×10^－5, if m_ν=0     

Ionization Energies of Ions in Hot and Dense Plasma: Beryllium-Like Ions for Z=26-36

Ionization energies of beryllium-like ions for Z = 26 - 36 in hot ana aense plasmas （ne=10^22 -10^24 cm^-3,kT= 500 - 2000 eV） are obtained by using an approach developed for electronic structure and transition property of ions in hot and dense plasmas based on the multi-configuration Dirac-Fock model. Influence of the plasma environment is considered by introducing a correction to the one-electron potential to account for the screening of the ionized electrons. This correction is calculated from the ionized electron micro-space distribution, which is obtained based on an ＂average atom model for the temperature and density-dependent average ionization of atoms in plasmas. Comparison between the present and the ion sphere models is made to display the significance of the ionized electron micro-space distribution.     

晶体PZCST:VO2+的EPR谱及光吸收谱的理论研究

采用双旋-轨耦合参量模型和3d¹电子组态在四角对称下的能级公式,计算了KZnClSO₄·3H₂O(PZCST): VO²⁺的EPR谱和光吸收谱,所得EPR谱和光吸收谱的理论结果与实验发现符合得很好. 研究发现,该晶体沿C₄轴局域对称结构呈压缩的四角畸变,其大小为0.47 nm;大的κ值表明VO²⁺的未配对电子的自旋极化对超精细结构常数有着较大的贡献.     

Defect generation in polycrystalline Cu(In,Ga)Se2 by high-energy electron irradiation

We investigate the degradation of ZnO/CdS/ Cu(In,Ga)Se₂ heterojunction solar cells for space applications and the defect generation in polycrystalline Cu(In,Ga)Se₂ thin films by irradiation with 1-MeV electrons with fluences J_e up to J_e=5᎒¹⁸ cm^-2. Notable degradation of the solar cell performance starts at fluences of J_e=10¹⁷ cm^-2 where the open circuit voltage decreases by about 5% while short circuit current and fill factor remain essentially unaffected. Thus, Cu(In,Ga)Se₂ solar cells withstand electron fluences which are higher by one order of magnitude or more when compared to other technologies. A model describes the absolute open circuit voltage loss considering the increase of space charge recombination by electron irradiation-induced defects. Defect analysis by admittance spectroscopy shows that acceptor defects with an energy distance of approximately 300 meV from the valence band are generated at a rate %=0.017 (ǂ.01) cm^-1.     

Band Gap Energies and Refractive Indices of Epitaxial Pb1-xSrxTe Thin Films

Pb1-x Srx Te thin films with different strontium （St） compositions axe grown on BaF2 （111） substrates by molecular beam epitaxy （MBE）. Using high resolution x-ray diffraction （HPLXRD）, we obtain Pb1-xSrxTe lattice constants, which vary in the range 6.462-6.492 A. According to the Vegard law and HRXRD data, Sr compositions in Pb1-xSrxTe thin films range from 0.0-8.0%. The Pb1-xSrxTe refractive index dispersions are attained from infrared transmission spectrum characterized by Fourier transform infrared （FTIR） transmission spectroscopy. It is found that refractive index decreases while Sr content increases in Pb1-xSrx Te. We also simulate the Pb1-xSrxTe transmission spectra theoretically to obtain the optical band gap energies which range between 0.320 e V and 0.449 e V. The simulated results are in good agreement with the FTIR data. Finally, we determine the relation between Pb1-xSrx Te band gap energies and Sr compositions （Eg = 0.320＋0.510x-0.930x^2 ＋184x^3 （eV））.     

Additivity Rule for Electron-Molecule Total Cross Section Calculations at 50-5000 eV： A Geometrical Approach

To quantify the changes of the geometric shielding effect in a molecule as the incident electron energy varies, we present an empirical fraction, which represents the total cross section （TCS） contributions of shielded atoms in a molecule at different energies. Using this empirical fraction, a new formulation of the additivity rule is proposed. Using this new additivity rule, the TCSs for electron scattering by CO2, C2H2, C6H12 （cyclo-hexane） and CsH16 （cyclo-octane） are calculated in the range 50-5000 e V. Here the atomic cross sections are derived from the experimental TCS results of simple molecules （H2, O2, CO）. The quantitative TCSs are compared with those obtained by experiments and other theories, and good agreement is attained over a wide energy range.     

Fine-Structure Splittings of Nitrogen Isoelectronic Sequence： Competitions among Spin-Orbit Interactions, Breit Interactions and Electron Correlations

Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration interaction method with quantum-electrodynamics corrections performed by the GRASP code, we calculate the fine-structure energy levels of the ground-state configuration （1s^22s^22p^3） of the nitrogen isoelectronic sequence, according to the L-S coupling scheme with atomic number Z up to 22. Based on the calculated results, we elucidate the mechanism of the orderings of fine-structure energy levels of 2^ D3/2,5/2 and 2^P1/2,3/2 respectively, i.e. for 2^D3/2,5/2 orderings, the competition between the spin-orbit interactions and the Breit interactions; for 2^P1/2,3/2 orderings, the electron correlations, especially the electron correlations owing to the 2p^5 configuration interactions.     

Laser-induced positive ion and neutral atom/molecule emission from single-crystal CaHPO4·2 H2O: The role of electron-beam-induced defects

We examine laser-induced ion and neutral emissions from single-crystal CaHPO₄·2 H₂O (brushite), a wide-band-gap, hydrated inorganic single crystal, with 248-nm excimer laser radiation. Both laser-induced ion and neutral emissions are several orders of magnitude higher following exposure to 2 keV electrons at current densities of 200 7A/cm² and doses of 1 C/cm². In addition to intense Ca⁺ signals, electron-irradiated surfaces yield substantial CaO⁺, PO⁺, and P⁺ signals. As-grown and as-cleaved brushite show only weak neutral O₂ and Ca emissions, whereas electron-irradiated surfaces yield enhanced O₂, Ca, PO, PO₂, and P emissions. Electron irradiation (i) significantly heats the sample, leading to thermal dehydration (CaHPO₄ formation) and pyrolysis (Ca₂P₂O₇ formation) and (ii) chemically reduces the surface via electron stimulated desorption. The thermal effects are accompanied by morphological changes, including recrystallization. Although complex, these changes lead to high defect densities, which are responsible for the dramatic enhancements in the observed laser desorption.     

Nanocrystalline growth and diagnostics of TiC and TiB2 hard coatings by pulsed laser deposition

Nanocrystalline coatings of TiC and TiB₂ were grown by pulsed laser deposition on Si(100) and on X155 steel at low substrate temperatures ranging from 40 °C to 650 °C. A pulsed KrF excimer laser was used with the deposition chamber at a base pressure of 10^-6 mbar. The morphology and structure of the films, studied with SEM, XRD, and TEM, showed that nanocrystalline films with a fine morphology of TiC and TiB₂ were deposited with a grain size of 10 nm-70 nm at all substrate temperatures. The growth of the polycrystalline coatings possessed a columnar morphology with a 𘜄¢ preferred orientation. The hardness of the coatings was determined to be 40 GPa and the elastic modulus, 240 GPa. The composition and the kinetics of the plume produced during the pulsed laser deposition of TiC and TiB₂ was studied under film growth conditions. The mass analysis of ions of the ejected material was performed by time-of-flight mass spectroscopy (TOF-MS) and showed the presence of Ti⁺ and C⁺ during TiC ablation and B⁺, B₂⁺, and Ti⁺ during TiB₂ ablation. The kinetic energies (KE) of the ions depended on the laser fluence which was between 0.5 eV and 340 eV. The kinetic energy and the evolution of the plasma was studied with a streak camera. The velocity of the plasma was of the order of 10⁶ cm/sec and was linearly dependent on the energy fluence of the laser. The emission spectroscopy of the plasma plume confirmed the atomic neutral and single excited species of Ti. These results show that coating growth basically occurs by the recombination of the ionic species at the surface of the substrate.     

因瓦合金纳米微粉的恒磁导率及其压力、频率特性和压力相变

 以Fe-30wt%Ni合金片为母合金，用蒸发冷凝法制备了三种粗细不同的纳米微粒。经透射电镜和X光衍射物相分析，微粒成分与母合金一致。5T、5H和3K粉的平均粒度分别为13.6、27和40 mm。在室温和43~28个不同的流体静压力（0.000 1~2.205 GPa）下测量了它们的磁化曲线、磁导率曲线和起始磁化曲线。结果表明：（1）在H＝(20－132)(1000/4π)A/m范围内Fe-30Ni合金三种纳米粉均具有恒磁导率。（2）三种纳米粉恒磁导率随静水压的变化规律如下：μ_r＝3.83+0.253p-0.022 1p²-0.007 22p³（5T粉）；μ_r＝3.93+1.20p-1.97p²+1.52p³-0.510p⁴+0.059 9p⁵（5H粉）；μ_r＝5.96-0.276p+0.107p²-0.045 9p³（3K粉）。前两者随压力增加而升高。后者随压力增加而下降。（3）γ-α马氏体相变明显存在于5T、5H粉中，而3K粉中未见到。（4）Fe-30Ni合金片的μ_i从200kHz至2 MHz已下降一个数量级，而其纳米粉μ_i的频率范围高于300 MHz，增大两个数量级以上。