Influence of Ba^2＋ and Pb^2＋ Ions on the Raman Dominating Active Vibronic Mode in Strontium Nitrate Crystals

The compositions of Sr(NO3)2 crystals grown from an aqueous solution doped with Ba^2 and Pb^2 were characterized by the electron probe microanalysis technique.It was found that Ba^2 is enriched in {100} sectors and Pb^2 in {111} sectors.The Raman spectra of different parts of these crystals at room temperature in the ranges of 1038-1070cm^-1 and 650-1150cm^-1 were investigated.The results indicated that barium and lead shift the Raman dominating peaks to the lower frequency and broaden the full width at half maximum.Furthermore,barium probably degrades the properties of the Sr(NO3)2 Raman shifter while lead is anticipated to improve it.     

Hydrogenation Properties of Zr Films Under Various Conditions of Hydrogen Plasma

The hydrogenation properties of Zr samples with and without an Ni overlayer under various plasma conditions were investigated by means of non-Rutherford backscattering and elastic recoil detection analysis.The theoretical maximum hydrogen capacity,66.7 at%,could be achieved at a hydrogen absolute pressure of-2Pa and a substrate temperature of-393K for a plasma irradiation of only 10min;this was significantly greater than that for gas hydrogenation under the same hydrogen pressure and substrate temperature.It was also found that the C and O contamination on the sample surface strongly influences the hydrogenation,and that the maximum equilibrium hydrogen content drops dramatically with the increasing total contamination.In addition,the influence of the Ni overlayer on the plasma hydrogenation is discussed.     

Modulation Spectroscopy of GaAs Covered by InAs Quantum Dots

Contactless electroreflectance has been employed at room temperature to study the Fermi level pinning at undoped-n^ GaAs surfaces covered by 1.6 and 1.8 monolayer (ML) InAs quantum dots (QDs).It is shown that the 1.8 ML InAs QD moves the Fermi level at GaAs surface to the valence band maximum by about 70 meV compared to bare GaAs,whereas 1.6 ML InAs on GaAs does not modify the Fermi level.It is confirmed that the modification of the 1.8 ML InAs deposition on the Fermi Level at GaAs surface is due to the QDs,which are surrounded by some oxidized InAs facets,rather than the wetting layer.     

Phase Dependence of the Inversionless Gain in a Λ System with Near—Degenerate Levels

Due to interaction with the vacuum of the radiation field,near-degenerate lower levels in a Λ system have an additional coherence term,the spontaneously generated coherence (SGC) term.For such a system,we investigate the effect of the relative phase between two coherent fields on the inversionless gain in the presence of the SGC.We find that the inversionless gain,which stems from both SGC and dynamically induced coherence,can be modulated by the relative phase.     

Weakly Two—Dimensional Solitary Waves on Coupled Nonlinear Transmission Lines

We study the nonlinear solitary wave solution under the transverse perturbations for a system of coupled nonlinear electrical transmission lines.In the continuum limit and suitably scaled coordinates,the voltage on the system is described by a modified Zakharov-Kuznetsov equation.The cut-off frequency of the growth rate for the solitary waves under transverse perturbations has been analytically obtained.It is in agreement with the cases P=1/2 and p=1 which have been studied previously.     

Effect of a Cr Underlayer on the Magnetic Properties of TbCo Amorphous FIlms with Perpendicular Anisotropy

The effect of the Cr underlayer on the magnetic properties of TbCo amorphous films with perpendicular anisotropy has been investigated.It was found that the Cr underlayer thickness can influence the coercivity of TbCo films.A coercivity as high as 6.3kOe was obtained in 120nm Tb31Co69 films with a 180nm Cr underlayer.This was only 4.4kOe for the same thickness Tb31 CO69 films without the Cr underlayer.Cross-sectional scanning electron microscopy indicated that the TbCo film with the Cr underlayer consisted of a Column structure.It is considered that this heterogeneous structure gives rise to the coercity enhancement of TbCo films in the presence of the Cr underlayer.     

Can Quintessence Be the Rolling Tachyon？

In the light of the recent works by Sen(hep-th/o203211,hep-th/0203265,hep-th/0204143)and Gibbons(hepth/0204008),we present a phase-plane analysis on the cosmology containing a rolling tachyon field in a potential resulting from string theory.we show that there is no stable point on the phase-plane,which indicates that there is a coincidence problem if we consider the tachyon as a candidate for quintessence.Furthermore,we also analyse the phase-plane of the cosmology cotaining a rolling tachyon field for an exactly solvable toy potential in which the critical point is stable.Therefore,it is possible for the rolling tachyon to be a candidate for quintessence if we give up the strict constraint on the potential or find a more appropriate effective potential for the tachyon from M/String theory.     

苄基保护甘露糖羧酸酯的NMR研究

应用NMR技术研究了1-0-(3,5-二硝基苯甲酰基)-2、3、4、6-四-0-苄基-D-吡喃甘露糖的α、β异构体的构型和糖环上碳氢归属情况,总结了苄基保护甘露糖羧酸酯构型的确证方法及影响糖环上碳氢化学位移的一些规律;并对其它13种四苄基甘露糖羧酸酯的NMR谱进行了研究,提供了这些化合物的¹³C和¹H NMR数据.     

《量子力学》自学辅导之十一——电子自旋（续）

《量子力学》自学辅导之十一──电子自旋（续）宋宇辰，曾心愉，裴文杰（１）复旦大学理论物理骨干教师班；２）复旦大学物理系，上海２００４３３）２．３自旋算符的矩阵形式自旋函数是２×１的矩阵，作用在自旋函数上的自旋算符应该是２×２的矩阵．设泡利算符的矩阵形...