Demonstration of a radio-frequency spectrum analyzer based on spectral hole burning

Spectral hole-burning (SHB) technology is considered for >10-GHz instantaneous bandwidth signal-processing applications. In this context we report on what is believed to be the first demonstration of a SHB microwave spectrometer. A set of gratings engraved in a SHB crystal is used to filter one sideband of the optically carried microwave signal. The setup is confined to narrow-bandwidth operation, over a 35-MHz-wide interval. The first findings confirm the validity of the architecture in terms of spectral resolution, angular channel separation, and simultaneous detection of multiple spectral lines.     

铝粉快速反应光谱中AlO B^2Σ^＋→X^2Σ^＋发射光谱的研究

在由光学多道分析仪收集的氢氧气体爆轰激励下铝粉快速反应光谱中，观察到ＡｌＯＢ２Σ＋→Ｘ２Σ＋跃迁Δｖ＝０带系的光谱特征与通常铝氧化反应的光谱特征不同。经分析是因为存在一个从４６７ｎｍ开始向长波方增强的连续辐射，它改变了该波长区ＡｌＯ分子的辐射特征。这一连续辐射可能是由铝与水蒸汽发生水合反应生成，而处于不同激发态的多原子分子ＨＡｌＯＨ产生     

水高温高密度状态方程理论研究

 采用MCR方法计算由exp-6势描述的水分子作用体系的pVT状态方程。与MD数值模拟结果比较后发现，由于水分子间强烈的吸引作用有利于分子有序化过程的发生，在较高温度（2 000~4 000 K）条件下，水分子作用体系仍呈现出固态特征。该物相区内体系的热力学性质不能用MCR理论描述但MCR理论准确预言了水分子作用体系高温液相区pVT状态方程。     

Selective attachment of benzaldehyde on Si(100)-2 x 1: structure, selectivity, and mechanism

The interaction of benzaldehyde with the Si(100) surface has been investigated as a model system for understanding the interaction of conjugated pi-electron systems with semiconductor surfaces. Vibrational features of chemisorbed benzaldehyde unambiguously demonstrate that the carbonyl group directly interacts with the Si surface dangling bonds, evidenced in the disappearance of the C=O stretching mode around 1713 cm(-1) coupled with the retention of all vibrational signatures of its phenyl ring. X-ray photoemission spectroscopy shows that both C 1s and O 1s binding energies of the carbonyl group display large downshifts by 1.9 and 1.3 eV, respectively. Vibrational and electronic results show that the covalent attachment of benzaldehyde on Si(100) occurs in a highly selective manner through the direct interaction of both C and O atoms of the carbonyl group with a Si=Si dimer to form a four-membered Si-C-O-Si ring at the interface, leaving a nearly unperturbed phenyl ring protruding into vacuum. This conclusion is further confirmed by the observation of a predominant protrusion for benzaldehyde adsorbed on Si(100)-2 x 1 in scanning tunneling microscopy experiments, consistent with the predication of density-functional theory calculation.     

Dry synthesis of triple cumulative double bonds (C=C=C=N) on Si(111)-7 x 7 surfaces

The interactions of cyanoacetylene and diacetylene with a Si(111)-7 x 7 surface have been studied as model systems to mechanistically understand the chemical binding of unsaturated organic molecules to diradical-like silicon dangling bonds. Vibrational studies show that cyanoacetylene mainly binds to the surface through a diradical reaction involving both cyano and C[triple bond]C groups with an adjacent adatom-rest atom pair at 110 K, resulting in an intermediate containing triple cumulative double bonds (C=C=C=N). On the other hand, diacetylene was shown to the covalently attached to Si(111)-7 x 7 only through one of its C[triple bond]C groups, forming an enynic-like structure with a C=C-C[triple bond]C skeleton. These chemisorbed species containing triple cumulative double bonds (C=C=C=N) and C=C-C[triple bond]C may be employed as precursors (or templates) for further construction of bilayer organic films on the semiconductor surfaces.     

三维多孔集流体改善NiO电极的储锂特性

三维多孔金属不仅可容纳电极在储锂过程中的体积变化,且为锂离子提供快速传输通道,因此被广泛用做锂离子电池集流体,以提升其循环稳定性和高倍率容量.NiO作为锂离子电池负极具有高理论比容量而备受关注,但其电子导电性差和充放电过程中的巨大体积变化造成其循环寿命短和高倍率容量低.此外,NiO首次放电（嵌锂）产物Ni⁰和Li₂O不能在充电（脱锂）过程中完全反应造成首次不可逆容量大,阻碍了其商业化应用.本工作采用简单、易规模化的化学镀法制备出具有三维贯穿孔的多孔铜（孔径≈5 μm）,并在其孔壁电沉积获得NiO@三维多孔铜电极.由于三维多孔铜集流体可容纳NiO储锂过程中的体积变化;为锂离子提供快速传输通道,同时其高比表面积增大了Ni⁰和Li₂O的反应活性点,因此该电极显示出优异的高倍率容量和高首次库伦效率.该电极在200 mA·g^-1电流密度下,首次放电（嵌锂）和充电（脱锂）容量分别为1522.3和1230.2 mAh·g^-1,首次库伦效率达到80.8%;在高电流密度20 A·g^-1下显示578.1 mAh·g^-1容量.以NiO@三维多孔铜为负极,LiNi_1/3Co_1/3Mn_1/3O₂为正极组装成全电池,首次充电和放电容量分别为1514和1060 mAh·g^-1（基于NiO电极,电流密度0.2 A·g^-1）,首次库伦效率为70%;1.0 A·g^-1电流密度下,首次放电比容量为873 mAh·g^-1,100次循环后保持709 mAh·g^-1,保持率为81%;10 A·g^-1电流密度下容量保持530.6 mAh·g^-1.该工作将为过渡金属氧化物储锂性能提升提供新途径.     

用四氨基铝酞菁共振光散射技术测定纳克级核酸

痕量核酸对四氨基铝酞菁的共振散射光产生增强作用,且增强程度与核酸浓度之间有良好的线性关系.据此建立了测定核酸的高灵敏共振散射光增强分析方法.在pH=6.0、最大散射波长400nm处,测定小牛胸腺DNA(CTDNA)、鲑鱼精子DNA(SMDNA)和酵母RNA(YeastRNA)的线性范围分别是0～250ng/mL,0～200ng/mL和0～400ng/mL,检测限分别为1.4ng/mL,1.4ng/mL和2.7ng/mL.该法简单,灵敏度高,用于实际样品中核酸含量的测定,所得结果与紫外吸收法一致.     

Asymptotic behavior and blow-up of solutions for infinitely degenerate semilinear parabolic equations with logarithmic nonlinearity

In this paper, we study the initial-boundary value problem for infinitely degenerate semilinear parabolic equations with logarithmic nonlinearity $u_t?{△}_{X}u=u\log ?|u|$, where $X=(X_1,X_2,?,X_m)$ is an infinitely degenerate system of vector fields, and ${△}_X:={\sum }_{j=1}^m{X}_j^2$ is an infinitely degenerate elliptic operator. Using potential well method, we first prove the invariance of some sets and vacuum isolating of solutions. Then, by the Galerkin method and the logarithmic Sobolev inequality, we obtain the global existence and blow-up at +∞ of solutions with low initial energy or critical initial energy, and we also discuss the asymptotic behavior of the solutions.     

慢电子被氧原子弹性散射的截面计算

采用Ｈａｒａ ｆｒｅｅ－ｅｌｅｃｔｒｏｎ－ｇａｓ ｅｘｃｈａｎｇｅ ａｐｐｒｏｘｉｍａｔｉｏｎ（ＨＦＥＧＥ）交换势和本文作者提出的极化势，用等效势模型计算了能量在０．１３６－１２ｅＶ内的ｅ－Ｏ弹性散射总截面和动量转移截面，结果与Ｔｈｏｍａｓ和Ｎｅｓｂｅｔ的理论计算结果以及实验结果作了比较。     

金属原子团簇与碳原子团簇的电子能谱与吸收光谱

此文从理论上阐明，金属原子团簇与具有π电子的碳原子团簇，其公有化电子不能视为无限自由的，而是肥边界约束的，因而其电子能谱不是连续能带，而具有分裂级的特性。因此，它们的共有化电子可吸收光子由低能级跃迁到高能级而具有吸光的特性。电子能级之间的间距视团簇的大小不同而有差异，调整团簇的大小，可吸收不同波长的光。利用这种特性，可设计所需要的红外与微波吸收材料，此文提出了这方面的新理论和设计原理。