Critical fields of (La.925Ba.075)2CuO4−y

We have measured the upper critical field of (La_.925Ba_.075)₂CuO_4-y in the range from 0 to 30 Tesla in the hybrid magnet at the Francis Bitter National Magnet Lab. The resistive transition in zero field onsets above 3 OK, with .9R_n at 29K, .1R_n at 27K and 0 below 24K (R_n = R(3 4K). Following the II-T curves for different fractions of R_n we find substantial differences in the temperature dependence of the apparent critical field. However, for (H,T)=.9R_n there is good agreement with simple pairbreaking behavior with an extrapolated H_c2(0) of 46 Tesla. At 4K there is no measurable resistance to 30 Tesla.     

Anomalous in-plane magnetoresistance of electron-doped cuprate La_(2.x)Ce_xCuO_(4±δ)

We report systematic in-plane magnetoresistance measurements on the electron-doped cuprate La_(2.x)Ce_xCuO_(4±δ) thin films as a function of Ce doping and oxygen content in the magnetic field up to 14 T. A crossover from negative to positive magnetoresistance occurs between the doping level x = 0.07 and 0.08. Above x = 0.08, the positive magnetoresistance effect appears, and is almost indiscernible at x = 0.15. By tuning the oxygen content, the as-grown samples show negative magnetoresistance effect, whereas the optimally annealed ones display positive magnetoresistance effect at the doping level x = 0.15. Intriguingly, a linear-field dependence of in-plane magnetoresistance is observed at the underdoping level x = 0.06, the optimal doping level x = 0.1 and slightly overdoping level x = 0.11. These anomalies of in-plane magnetoresistance may be related to the intrinsic inhomogeneity in the cuprates, which is discussed in the framework of network model.     

LaNi_5和LaNi_(4 .7)Al_(0 .3)氢化物柱内氢氘间的排代

进行了室温附近LaNi5和LaNi4 .7Al0 .3 两种材料上气 固间氢氘的排代实验。两种材料的排代效果都较好 ,相比之下 ,LaNi5的更优。可以推测 ,在不要求得到高纯氚的情况下 ,都可以用作氚的冷卸载贮存床。初步的理论探讨揭示 ,气 固界面的化学交换反应是产生排代效应的原因 ,宏观交换规律决定排代效果。理想化的塔板理论模型对排代流出曲线的描述是有效和适用的 ,塔板高度是材料排代性能优劣的指标 ,在确定的排代条件下 ,如果塔板高度小于 1.0cm ,应该认为具有较好的排代效果。     

E.P.R. study of γ-irradiated single crystals of K2C2O4.H2O and (NH4)2C2O4.H2O

The electron paramagnetic resonance of γ-irradiated single crystals of K₂C₂O₄.H₂O and (NH₄)₂C₂O₄.H₂O has been studied. The spectra show interesting microwave power saturation effects. The singlet spectrum is attributed to the C₂O₄ ^- radical derived from the C₂O₄ ^-- ion. The principal g-values are determined to be 1·998, 2·0028 and 2·0004. Certain weak lines are observed with different power saturation and interpreted as due to OH radicals derived from water molecules in the crystal lattice.     

SU(4)×SU(4)禁闭弱作用复合模型

本文对超色群为半单群的亚夸克模型结构作了讨论, 具体构造了一个SU(4)×SU(4)禁闭弱作用复合模型, 模型中给出了三代轻质量的复合粒子.     

Conformational Studies of 1-(2′-Hydroxythiobenzoyl)piperidine and 4-(2′-Hydroxythiobenzoyl)morpholine by High Resolution N.M.R. Spectroscopy

Abstract

The 220 MHz ¹H nmr spectra of the title compounds (1a) and (2a), respectively, at low temperature in CDCl₃ solution are interpreted in terms of two interconverting chair forms with unequal populations (K_e = 1.17, δG° ～70 cals/mole for 1a and K_e = 1.8, δG° ～0.2 kcal/mole for 2a at ?30°C). A strong intramolecular OH…S hydrogen bond in both compounds reduces the number of degrees of freedom of the bulky N-thiobenzoyl substituent, which nearly eclipses the equatorial α-CH₂ hydrogen atoms in both comformations. Steric interactions between the 6′ phenyl proton and the hetero-ring α-CH₂ protons trans to the thiocarbonyl group are different in the two conformations of la and 2a.     

有机材料(EDT-DSDTFVO)FeCl_4和(EDT-DSDTFVO)GaCl_4的输送现象

通过对有机材料(EDT-DSDTFVO)2FeCl4和(EDT-DSDTFVO)2GaCl4的输送测定,对其电阻率的温度依赖性以及压力效果进行了系统的比较,虽然两类盐的电阻率随着温度的变化行为十分相似,但是其压力效果尤其在高压时表现出明显的差异性。认为这种差异性和π-d相互作用密切相关。在这里,用EDT-DSDTFVO表示ethylenedithiodiselenadithiafulvalenothioquinone-1,3-dithiole methide。     

N(~4S_u) CH(a~4∑~-)体系的分子反应动力学研究

用轨线法对Ｎ（４Ｓｕ）＋ＣＨ（０，０）→ＣＮ（ｖ′，Ｊ′）＋Ｈ（２Ｓｇ）和Ｎ（４Ｓｕ）＋ＣＨ（０，０）→ＮＨ（ｖ′，Ｊ′）＋Ｃ（３Ｐｇ）反应进行计算，研究了两个反应的阈能、反应截面、产物散射分析和微观反应机理     

有机材料(EDT-DSDTFVO)FeCl4和(EDT-DSDTFVO)GaCl4的磁电阻分析

有机材料(EDT-DSDTFVO)2FeCl4和(EDT-DSDTFVO)2GaCl4的输送实验结果,显示出这两类盐的电阻率对温度的依赖性以及压力效果十分相似,但是两种盐的磁电阻率却表现出很大的不同,FeCl4盐为负磁电阻,而GaCl4盐为正磁电阻.我们认为这种输送现象的差异性起源于π-d相互作用.我们用EDT-DSDTFVO表示ethylenedithiodiselenadithiafulvalenothioquinone-1,3-dithiole methide.     

Na5Eu(MoO4)4和Na5Eu(WO4)4的荧光光谱和晶场参数

本文报告了Na5Eu(MoO4)4和Na5Eu(WO4)4粉末样品的荧光光谱。结果表明,在这些化合物中,稀土离子占据S4对称性晶格点,点对称性相当接近D2d。从实验光谱数据,我们导出了D2d对称性下Na5Eu(MoO4)和Na5Eu(WO4)4的晶场参数,这些参数相当好地拟合了从光谱实验中得到的能级。     

Similarities in the decomposition and dehydrogenation of cyclohexene on (4 × 4)-CMo(110) and Pt(111)

The decomposition and dehydrogenation of cyclohexene have been used as probing reactions to directly compare the surface reactivities of carbon-modified Mo(110) and Pt(111). By using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS), we find that the dominant decomposition pathway of cyclohexene can be converted from complete decomposition to atomic carbon and hydrogen on clean Mo(110) to partial dehydrogenation to benzene and hydrogen on (4 × 4)-CMo(110). The latter reaction mechanism is very similar to that observed on Pt(111). Furthermore, in contrast to the near identical catalytic properties that are commonly observed for bulk molybdenum carbide and nitride powder materials, we find that the reactivities of carbon-modified and nitrogen-modified Mo(110) surfaces are qualitatively different.     

2002 (Vol.16)AUTHOR INDEX

ＢＢＡＩＪｉｎｇ ｓｏｎｇ　　　　　 1 6 (3 ) 2 0 4ＢＡＩＳｈｕｏ 1 6 (1 ) 42ＢＡＯＺｈｏｎｇ ｘｉｎｇ 1 6 (1 ) 421 6 (2 ) 1 3 7ＣＣＡＩＬｉｎｇ ｃａｎｇ 1 6 (1 ) 6 11 6 (4) 2 4 9ＣＡＯＪｕ ｚｈｅｎ 1 6 (3 ) 1 99ＣＡＯＬｉ ｍｉｎ 1 6 (3 ) 2 2 4ＣＨＡＮＧＷｅｎ ｗｅｉ 1 6 (2 ) 1 47ＣＨＥＮＣｈａｎｇ ａｎ 1 6 (2 ) 1 40ＣＨＥＮＤｏｎｇ ｑｕａｎ 1 6 (1 ) 6 1ＣＨＥＮＧＨｕｉ ｍｉｎｇ 1 6 (1 ) 42ＣＨＥＮＧＳｈｕ ｘｉａ 1 6 (4) 3 0 5ＣＨＥＮＨａｉ ｙｏｎｇ 1 6 (3 ) 1 83ＣＨＥＮＱｉ ｆｅｎｇ 1 6 (1 ) 6 1…     

2002 (Vol.16)SUBJECT INDEX

ＴｈｅｏｒｅｔｉｃａｌＳｔｕｄｉｅｓａｎｄＮｕｍｅｒｉｃａｌＭｏｄｅｌｉｎｇＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＩｎｉｔｉａｔｉｏｎｏｆＰＢＸ 940 4ＩｍｐａｃｔｅｄｂｙＲｏｕｎｄ ＮｏｓｅｄＳｔｅｅｌＰｒｏｊｅｃｔｉｌｅｓ　　ＺＨＥＮＧＰｉｎｇ ｇａｎｇ ,ＺＨＡＯＦｅｎｇ ,ＺＨＡＮＧＺｈｅｎ ｙｕ………………………………………… 1 6 (1 ) 2 9ＴｈｅＤｙｎａｍｉｃＭｏｄｅｌｏｆＶｉｔｒｅｏｕｓＣａｒｂｏｎｕｎｄｅｒＳｈｏｃｋＬｏａｄｉｎｇ ＷＵＣｈｅｎｇ ,Ｙ .Ｍ .Ｇｕｐｔａ……1 6 (1 ) 3 4Ｎｕｍ…     

SUPERCONDUCTIVITY IN La_(1.85)Sr_(0.15)Cu_(1-x)Zn_xO_4

Based on the multiple exchange-mediated interaction mechanism of high- Tc superconductivity and the Abrikosov-Gorkov theory of magnetic impurity superconductors, this paper quantitatively explains the Zn-substitution experiment of La1.85Sr0.15Cu1-x ZnxO4.