奇A 核的多声子γ振动带实验研究进展

对于近年来清华大学与美国合作研究组在原子核结构实验研究中有关奇A 核的多声子 振动带方面的进展进行了评述。研究人员通过有效的国际合作,识别了质量数A = 100 丰中子核区的奇A核103Nb,105Mo,107Tc 和109Tc中的两声子 振动带,这是迄今为止国际上在奇A 核的结构研究中发现的仅有的4 例这样的结构。对于实验方法、研究结果以及这些多声子 振动带的特性进行了评述,并对目前在多声子带其他方面的研究及今后进一步的工作进行了概述。The experimental research on multi-phonon γ-vibrational bands in odd-A nuclei by our international collaboration has been reviewed. The two phonon -vibrational bands in 103Nb, 105Mo, 107Tc and 109Tc in the A = 100 neutron-rich nuclear region were identified, which are the only four such bands discovered in nuclear structure studies until now. The experimental methods and results are summarized, and the characteristics for these band structures are discussed. The other aspects for our research on the multi-phonon vibrational bands as well as our future research work are also briefly reviewed.     

用AFM和XPS研究LiBq4/ITO的表面和界面

用原子力显微镜(AFM)研究了LiBq4／ITO样品表面形貌,结果表明LiBq4层中存在很多裂缝和空隙。用X射线光电子谱(XPS)研究样品表面和界面的电子状态,发现Cls谱在高结合能端出现氧化特征的肩峰,表明真空蒸发沉积的LiBq4分子存在明显的氧化现象;对Bls谱的分析发现,界面处B原子的相对值远低于理论值,说明界面处存在B原子离解,导致了LiBq4分子的更高氧化态;从Cls谱发现,表面污染C的比例很高,而界面处大为下降,原因是表面吸附了气体,从而证实了LiBq4表面存在大量空隙和裂缝。定量研究发现,界面处存在N原子与In、Sn原子的相互作用,这将影响LiBq4的发光颜色。     

对互为反函数图象对称关系的证明过程的注记

关于函数与其反函数的图象间的对称关系有:定理　函数y=f(x)的图象与其反函数y=f-1(x)的图象关于直线y=x对称.从教材[1]上对其证明过程来看,证明了两个结论:1.函数y=f(x)图象上任一点M关于直线y=x的对称点M′都在y=f-1(x)的图象上;同时,2.函数y=f-1(x)图象上任一点关于直线y=x的对称点也都在y=f(x)的图象上.若仅仅证明结论1,可否说明y=f(x)与y=f-1(x)图象关于直线y=x对称?回答是否定的,事实上,只要对本节(P62)中例1稍作改造,就构造出一个反例:y=3x-2(x∈R ),y=x 23(x∈R)易见对y=3x-2(x∈R )图象上任一点,关于直线y=x的对称点都在y=x 23…     

碱木质素超/亚临界乙醇体系解聚机理研究

采用微型高温高压反应釜,在超/亚临界乙醇体系,进行麦草碱木质素的解聚实验,通过扫描电子显微镜(SEM)、气相色谱/质谱联用仪(GC/MS)及红外光谱仪(FT-IR)对解聚产物进行分析,探讨大分子结构的解聚机理。结果表明,碱木质素在乙醇临界点条件(240℃,7.2 MPa)解聚获得最低残焦得率,数值为16.5%。碱木质素在亚临界乙醇体系解聚过程,碱木质素熔融形成直径1.0-2.0μm的微球分散于乙醇中,结构单体间少量醚键和苯环侧链Cα均裂断裂,形成酚类、酯类、酮类和酸类产物;碱木质素在超临界乙醇体系解聚过程,熔融微球直径明显缩小,解聚时发生大量结构单体间醚键、苯环侧链Cα断裂及酯类产物的二次分解反应,解聚产物中酯类产物含量(11.94%)降低,酚类产物得率(52.14%)提高。     

Measurement of Angular Distribution for the ^8Li（p,d）^7Li Reaction

The ^8Li（p, d）^7 Li reaction plays an important role in the inhomogeneous Big Bang nucleosynthesis and in the seed-nuclide production phase for the r-process. For the first time, its angular distribution at backward angles was measured in inverse kinematics at Ec.m.=4.0 MeV by using an ^8Li secondary beam. The result of measurement includes the contributions of ^8Li（p, d0）^7Li and ^8Li（p, d1）^7Li^＊. The ^8Li（p, d0）^7Li component is estimated to be 40%-58% in the mixture angular distribution by analysing the measured result.     

Probing Field Emission from Boron Carbide Nanowires

High density boron carbide nanowires are grown by an improved carbon thermal reduction technique. Transmission electron microscopy and electron energy lose spectroscopy of the sample show that the synthesized nanowires are B4 C with good crystallization. The field emission measurement for an individual boron nanowire is performed by using a Pt tip installed in the focused ion beam system. A field emission current with enhancement factor of 10^6 is observed and the evolution process during emission is also carefully studied. Furthermore, a two-step field emission with stable emission current density is found from the high-density nanowire film. Our results together suggest that boron carbide nanowires are promising candidates for electron emission nanodevices.     

Mass Spectrometry Investigation on Decamethylcyclopentasiloxane Electron Cyclotron Resonance Plasma for SiCOH Film Deposition

We investigate the fragmentation behaviour of decamethylcyclopentasiloxane （DMCPS） plasma using a quadrupole mass spectrometry, which is used as the precursor to deposit SiCOH film in an electron cyclotron resonance （ECR） plasma system. The structure of DMCPS molecules comprises a fivefold Si-O ring and ten -CH3 groups bonded at five Si atoms. In ECR discharge plasma, the main fragmentation behaviour of DMCPS includes two stages. One is the breaking of fivefold Si-O rings and then the formation of threefold Si-O rings and Si-O chain species. The other is the decomposing of hydrocarbon groups from Si atoms and then the crosslink of hydrocarbon species. Combined with the bonding configuration of SiCOH films, the relation between species in ECR plasma and films structures is analysed.     

通过自由基串联环化反应合成4-喹诺酮类化合物

4-喹诺酮结构广泛存在于天然产物和药物分子中. 本工作以易得的N-芳基-O-炔丙基氨基甲酸酯为原料, CO为羰基源, 发展了一种高效、模块化合成4-喹诺酮结构的方法. 氨基甲酸酯底物经2-碘酰基苯甲酸(IBX)氧化产生酰胺氮自由基, 进而发生自由基串联环化反应得到4-喹诺酮结构.     

基于高阶角向偏振拉盖尔高斯涡旋光束强聚焦的三光链结构

依据角向偏振涡旋光束强聚焦有径向分量的结论,修正了角向偏振涡旋光束的强聚焦场公式,重新研究了高阶角向偏振拉盖尔高斯涡旋光束经过衍射光学元件和高数值孔径透镜后的强聚焦特性。结果发现,在焦平面附近获得了新的三维三光链结构(沿着光轴方向的一条三维主光链和对称的两条三维傍轴次光链),详细分析了入射光束缔合拉盖尔多项式的径向模数和光束的拦截比、衍射光学元件结构和聚焦系统的数值孔径对三光链的影响。结果表明,径向模数的改变会破坏三光链结构,通过调控衍射光学元件结构和拦截比可以重新获得对称性更高的三光链结构,从而实现对三光链结构的高自由度调控。