Highlights from the COMPASS experiment

The Compass experiment at CERN is studying the nucleon spin structure with a 160 GeV polarized muon beam and polarized targets as well as hadron structure with 190 GeV pion, kaon and proton beams. The paper gives an overview of the results for the helicity and transverse spin structure of the nucleon. A first result from the spectroscopy experiments, the observation of a resonance with exotic JPC = 1- + quantum numbers at 1660 MeV is also presented. The paper ends with an outlook to future measurements.     

双光束对高能电子的捕获特性

为了在实验上增强非线性强场效应的信号强度,基于电子在强激光束上的非弹性散射,提出一种双光束捕获电子的方案,目的是通过延长电子和强场相互作用时间来提高非线性过程发生总概率,实现观测信号的增强。数值模拟结果表明,捕获后的电子和强激光场的相互作用时间可延长10倍以上。     

The inverse electromagnetic scattering problem by a penetrable cylinder at oblique incidence

In this work, we consider the method of non-linear boundary integral equation for solving numerically the inverse scattering problem of obliquely incident electromagnetic waves by a penetrable homogeneous cylinder in three dimensions. We consider the indirect method and simple representations for the electric and the magnetic fields in order to derive a system of five integral equations, four on the boundary of the cylinder and one on the unit circle where we measure the far-field pattern of the scattered wave. We solve the system iteratively by linearizing only the far-field equation. Numerical results illustrate the feasibility of the proposed scheme.     

Change of the short-range scattering in the graphene covered with Bi2O3 clusters

In this work, we have studied the oxidation process of the bismuth doped graphene in the ambient air. Complete oxidation of the bismuth clusters and that of the graphene are firmly confirmed. The influence of oxygen on the graphene is characterized by means of Hall measurement and SdH oscillation. All transport measurements demonstrate a hole-type doping behavior. Our work also demonstrates that the short-range scattering mechanism is enhanced in doped graphene due to accumulated O-species adsorbates after being exposed in the atmosphere for 40 days and is suppressed after annealing. This investigation may open a new perspective for fabricating the graphene metal oxide devices.     

PATP在Ag/TiO_2纳米管基底上的表面增强拉曼散射和光催化过程研究

表面增强拉曼散射(SERS)是一种超灵敏、高选择性的分析方法,越来越受到人们的关注。对巯基苯胺(PATP)由于其易吸附在大多数SERS基底表面,并可以产生极强的SERS信号,因此常被用作SERS的探针分子。二氧化钛(TiO_2)是一种目前常用的光催化剂,但是其催化效率仍有待提高。将贵金属与TiO_2复合是提高其催化效率的有效手段。本文采用电化学阳极氧化法制备了二氧化钛纳米管(TiO_2NTs),并采用光化学还原方法在表面沉积了贵金属银,制备了一种同时具有SERS和催化性能的双功能基底,即银纳米粒子修饰的二氧化钛纳米管(Ag/TiO_2NTs),研究了PATP分子在该基底上的光催化过程,并与在银镜基底上的光催化过程进行了比较。我们发现,Ag/TiO_2NTs基底上的PATP在催化过程中峰强度逐渐减弱,但没有新峰的出现;而在银镜基底上PATP的峰强度随光照时间却几乎没有变化,证明了PATP分子在Ag/TiO_2 NTs上的光催化降解过程。本文还对Ag/TiO_2NTs上PATP的催化过程进行了动力学分析,结果表明PATP在该基底表面的催化反应为一级反应。     

显微激光拉曼定量分析CO_2气体碳同位素组成方法研究

制备了一系列不同比例的~(12)CO_2/N_2和~(13)CO_2/N_2混合物,对样品进行显微激光拉曼测试分析后发现气体拉曼特征峰峰面积比与其摩尔分数比成正比例关系,拟合方程的斜率被认为是拉曼量化因子F_(12CO_2)和F_(13CO_2)。用气相组分中只含有~(12)CO_2和N_2的流体包裹体验证了当F_(12CO_2),为1.163 49时,根据气体的拉曼特征峰峰面积比能估算出其摩尔分数比。由线性拟合后的方程斜率得出F_(13CO_2)和F_(12CO_2)分别为1.610 86和1.163 49,它们的比率F_(13CO_2)/F_(12CO_2)是1.3845。在确定稳定同位素分子的拉曼参数和实验条件基础上,CO_2气体碳同位素摩尔分数比C_(12)/C_(13)可根据A_(12Co_2)/A_(13CO_2)(拉曼峰峰面积比)和F_(13CO_2)/F_(12CO_2)的乘积求出。此外,用已知摩尔分数比(C_(12)/C_(13))的人造包裹体验证了此方法具有一定的可行性,可以建立起定量分析CO_2气体碳同位素激光拉曼测试方法。     

贵金属纳米结构为敏感层的锥形光纤探针及其SERS活性

表面等离激元纳米结构与便携式光纤拉曼系统相结合,在液体样品和生物活体组织的快速、实时监测上有较好的应用前景。其核心技术是将具有表面增强拉曼散射(SERS)活性的贵金属纳米结构耦合到光纤探针表面。本文基于共价键结合原理,将3-巯丙基三甲氧基硅烷通过与锥形光纤探针表面的硅羟基形成共价键修饰在光纤上;同时,硅烷偶联剂末端的巯基与金或银纳米结构形成Au-S或Ag-S共价键,将金纳米粒子和银纳米立方体牢牢吸附到光纤探针表面。这种SERS光纤探针具有很高的稳定性(SERS信号相对标准偏差低于3%),对农残甲基对硫磷的敏感度达到10纳摩尔,对污染物的远程、便携式在线检测具有重要意义。     

Compton散射下横等离激元与对等离子体作用特性

应用多光子非线性Compton散射模型、横等离激元色散方程和Karpman方法,研究了Compton散射对横等离激元与对等离子体作用特性的影响,提出了将入射超强激光和Compton散射作为横等离激元与对离子等离子体非线性作用新机制,给出了横等离激元非线性控制方程、等离激元数和能量公式。结果表明:与散射前相比,Compton散射使等离子体密度发生剧烈扰动,高频横等离激元与低密度扰动耦合非线性增强,导致横等离激元落入低密度区的几率增大。等离子体非线性频移和高密度区能量增加,低密度区能量减小,导致横等离激元电场包络迅速坍塌,等离激元数增加,场强度更强。