Identifying the Conformational Isomers of Single-Molecule Cyclohexane at Room Temperature

构象异构是化学中的基本问题。然而对于环己烷等柔性分子，由于其在室温下极快的互变异构过程，基于系综的表征方法（如核磁等）只能得到所有构象平均贡献的结果。为了应对这一挑战，化学化工学院洪文晶教授与夏海平教授课题组为在室温条件下对柔性分子构象的定量分析与表征这一挑战，课题组成功实现了在室温条件下对环己烷两种椅式构象的电学表征与比例识别。同时，通过纳米电极间隙对分子的限域作用，发现在宏观尺度下极不稳定的扭船式中间体得以在单分子尺度稳定存在，这为不稳定中间体的研究提供了重要表征方法。 这一研究工作是在化学化工学院洪文晶教授、夏海平教授共同指导下完成的，iChEM直博生唐淳与化工系研究生唐永翔为论文共同第一作者。师佳副教授与刘俊扬副研究员为该工作提供了指导，博士后陈志昕、博士研究生陈李珏以及研究生叶艺玲、严哲玮、张珑漪共同参与了该工作。【Abstract】Isomerism reflects the ubiquitous nature that molecules with the same molecular formula show different structures. The interconversion between conformational isomers of flexible molecules is quite fast owing to the low barriers of around 10 kcal mol−1, leading to average signal contributed by all the possible isomers characterized by ensemble methods. On this account, identifying the conformational isomers of flexible molecules at room temperature has a substantial challenge. Here, we develop a single-molecule approach to identify the conformational isomers of cyclohexane at room temperature through the single-molecule electrical characterization. By noise analysis and feature extraction of the conductance of single-molecule junctions, we quantificationally identified two chair isomers of cyclohexane at room temperature, while such identification is only feasible at low temperatures by ensemble characterization. The strategy to apply the single-molecule approach to identify conformational isomers paves the avenue to investigate the isomerization of flexible molecules beyond the ensemble methods.This work was supported by the National Natural Science Foundation of China (nos, 21722305, 21673195, 21703188, and U1705254), the National Key R&D Program of China (2017YFA0204902), China Postdoctoral Science Foundation (no. 2017M622060), and the Fundamental Research Funds for Xiamen University (20720190002).该工作获得了科技部国家重点研发计划、国家自然科学基金等项目的资助，也得到了固体表面物理化学国家重点实验室、能源材料化学协同创新中心的支持

Electric-field-induced selective catalysis of single-molecule reaction

随着单分子电学检测技术的迅速发展，分子电子学的研究不再局限于分子电子学器件的构筑及其电学性质的测量，而且扩展到单分子尺度化学反应过程的探索。然而目前相关的研究仍然局限于理论计算方面，在单分子尺度上实时监测和调控化学反应的活性和选择性是化学领域的长期目标和挑战。针对这一挑战，洪文晶教授课题组与程俊教授课题组合作，自主研发了精密科学仪器，将单个有机分子定向连接在两个末端尺寸为原子级的电极之间，解决了化学反应中分子取向控制的问题.理论计算结果证实了定向电场可以有效地稳定化学反应的过渡态，从而降低反应能垒。该研究工作在化学化工学院洪文晶教授、程俊教授、能源材料化学协同创新中心（iChEM）刘俊扬副研究员的共同指导下完成，由硕士研究生黄晓艳、iChEM博士研究生唐淳、博士研究生李洁琼以及兰州大学的陈力川博士作为共同第一作者，化学化工学院师佳副教授、陈招斌高级工程师、夏海平教授和田中群教授，萨本栋微纳研究院杨扬副教授、环境与生态学院白敏冬教授以及兰州大学张浩力教授参与了研究工作的讨论并给予指导，博士后乐家波、博士研究生郑珏婷、张佩（已毕业）、李瑞豪、李晓慧也参与了研究工作。Oriented external electric fields (OEEFs) offer a unique chance to tune catalytic selectivity by orienting the alignment of the electric field along the axis of the activated bond for a specific chemical reaction; however, they remain a key experimental challenge. Here, we experimentally and theoretically investigated the OEEF-induced selective catalysis in a two-step cascade reaction of the Diels-Alder addition followed by an aromatization process. Characterized by the mechanically controllable break junction (MCBJ) technique in the nanogap and confirmed by nuclear magnetic resonance (NMR) in bottles, OEEFs are found to selectively catalyze the aromatization reaction by one order of magnitude owing to the alignment of the electric field on the reaction axis. Meanwhile, the Diels-Alder reaction remained unchanged since its reaction axis is orthogonal to the electric fields. This orientation-selective catalytic effect of OEEFs reveals that chemical reactions can be selectively manipulated through the elegant alignment between the electric fields and the reaction axis.This work was supported by the National Key R&D Program of China (2017YFA0204902), the National Natural Science Foundation of China (21722305, 21703188, 21673195, 21621091, 51733004, 51525303, and 91745103), the China Postdoctoral Science Foundation (2017M622060), and the Young Thousand Talents Project of China. 该工作得到国家自然科学基金委（21722305、21703188、21673195、51733004、51525303、91745103），国家重点研发计划课题（2017YFA0204902），中国博士后面上基金（2017M622060）的资助，以及固体表面物理化学国家重点实验室、醇醚酯化工清洁生产国家工程实验室、能源材料化学协同创新中心的支持

HIRFL剥离器后切束线物理设计

HIRFL is a tandem cyclotron complex for heavy ion. On the beam line between SFC and SSC, there is a stripper. Behind it, the distribution of charge states of beam is a Gauss distribution. The equilibrium charge state Q_0 is selected by 1BO2(a 50° dipole behind the stripper) and delivered to SSC. One of two new small beam line (named SLAS) after 1B02 will be builded in or der to split and deliver the unused ions of charge states (Q_0 ± n) to aspecific experimental area. Q_0 ± n ions are septumed and separated from initial(Q_0) ion beam by two septum magnets SM1, SM2. The charge state selected by SM1 will be Q_0 ± 1(6 ≤ Q_0 < 17), Q_0 ± 2(17 ≤ Q_0 < 33) and Q_0 ± 3 (Q_0 ≥ 33) forming a beam in one of the two possine new beam line with the stripping energy of (0.2 to 9.83 Mev/A), an emittance of 10π mm.mrad in the two transverse planes and an intensity ranging from 10~(11) pps for z ≤ 10 to some 10~5 pps for the heaviest element. Behind SM2, a few transport elements (three dipoles and seven qudrupoles) tra nsport Q_0 ± n beam to target positions T1, T2 (see fig. 1) and generate small beam spots (φ ≤ 4mm, φ ≤ 6mm). The optics design of the beam line has been done based on SLAC-75 (a first and second - order matrix theory). beam optics calculation has been worked out with the TRANSPORT program. The design is a very economical thinking, because without building a new accelerator we can obtain a lower energy heavy ion beam to provide for a lot of atomic and solid state physical experiment

加速器束流非线性传输的逆变换

基于文献［１］，推导出普遍的非线性微分方程任意阶解的逆变换，从而在理论上实现了非线性动力学系统相空间的非线性传输。这个方法适于普遍的非线性动力学各个学科，加速器束流传输就是一个突出实例。Based on tge any order analytical solution of accelerator beam dynamics,is developed thegeneral theory for nonlinear transport of accelerator beam phase space,by inverse transformationmethod。The method is general by itself,and hence can alse be applied to the nonlinear transportof various dynamic systems in physics, chemistry and biology

兰州重离子加速器冷却储存环射频堆积过程模拟

考虑了重离子冷却储存环中粒子纵向相振荡的运动特性及电子冷却的作用 ,模拟兰州重离子加速器冷却储存环 (HIRFL CSR)主环中的射频堆积过程 ,给出了高频参数在射频堆积过程中随时间的变化曲线 ,为高频腔的设计及机器运行时的参数预置提供了理论依

重离子束注入同步加速器的方法及其装置

<p><font face="宋体" size="3">发明主要涉及将回旋加速器提供的质量数小于等于40的非全剥离重离子束流注入到同步加速器中的方法及其装置。一种重离子束注入同步加速器的方法，包括有如下步骤：1.将未被全剥离的量数小于或等于40重离子束加速到能量为5.0-10.0MeV/u，重离子束流强为2.0-6.0微安；2.将步骤1中质量数小于或等于40的重离子束偏转到剥离膜，并将同步加速器的中心轨道在注入点的位置凸起到剥离膜处；3.降低步骤2中所述的中心轨道的凸起，剥离后的重离子束注入并填充加速器空间，在同步加速器中作回旋运动。并提供一种重离子束注入同步加速器的装置。设备简单，操作方便，注入效率高的优点，并可以通过调整剥离膜厚度实现重离子束流电荷态的多种选择。</font></p

强流离子束的束包络方程与束包络计算——Ⅰ.强流离子束的束包络方程

在考虑了强流离子束自身空间电荷效应和束流初始特征(束流发射度)的情况下,本文给出了强流离子束在电磁场中运动的束包络方程.同时也给出了强流离子束分别在静电场、静磁场和自由空间(即等位空间)中运动的束包络方程

串级回旋加速器与冷却储存环系统

本发明涉及一种串级回旋加速器与双冷却储存环系统。包括有离子源 (500)和对称磁聚焦结构的冷却储存环(300)，对称磁聚焦结构的冷却储存环(300)注入端通过第一离子束输送线(600)与扇聚焦回旋加速器(100) 或/和分离扇聚焦回旋加速器(200)相接，对称磁聚焦结构的冷却储存环 (300)引出端通过第二离子束输送线(700)与非对称磁聚焦结构的冷却储存环(400)相接。其采用一台或多台回旋加速器的级联组合、一个用于提高离子束流品质的带离子冷却技术装置的同步加速器储存环，同样也采用离子冷却技术装置的冷却储存环，有效满足高精度核物理试验及原子物理实验，并可应用于材料辐照、质子-重离子治癌等应用性研究项目