峰形模拟在纳秒强激光电离碘甲烷团簇质谱中离子来源分析的应用

运用飞行时间质谱的峰形模拟程序，对纳秒强光场下CH₃I团簇电离过程中得到的离子峰进行模拟。根据模拟峰形与实验峰形的相似程度，直接反演出离子产生时的速度分布或空间分布，并根据速度或空间分布推测了离子产生的来源，其中C²⁺, I²⁺和I³⁺来源于库仑爆炸过程，C⁺, CH_x⁺⁽x=1,2,3), I⁺和CH₃I⁺来源于多光子电离过程，H⁺来源于上述两种过程，而少部分I⁺来源于电子碰撞电离。此外，通过峰形模拟，对离子的接收比例进行了研究。     

天然同位素信息在多级质谱裂解规律解析中的应用——以磺胺类化合物为例

为了更好的对多级质谱裂解信息进行解析,本研究在多级质谱中应用同位素峰信息进行分子式确证。使用二级质谱中同位素峰丰度比例和峰形信息,对化合物的质谱裂解碎片分子组成进行预测和推断。通过改变LTQ Orbitrap XL仪器的离子阱参数,将isolation width设为6 u,使目标母离子的最轻同位素峰和两个较重同位素峰共同裂解,报道了在二级质谱中获得目标化合物的同位素信息,并使用这些信息对化合物裂解碎片进行推测。以磺胺甲基嘧啶为例,通过同位素信息提供的丰度比和峰形信息,对主要裂解碎片离子进行解析,大多数结果与文献报道的裂解途径一致,但对于磺胺甲基嘧啶二级质谱中m/z 65的碎片离子,与已发表的文献报道不同,通过高分辨质谱和同位素丰度比的佐证,重新对其进行了解析,证明这是一个不含硫元素的子离子。结果表明,该方法能够有效减少分子式推测过程中产生的错误备选结果,可以为多级质谱的解析提供更准确的依据。     

《质谱学报》第27卷（2006年）总目次

第27卷第1期飞行时间质谱的离子峰形模拟分析方法和应用…………………………温丽华,李海洋,牛冬梅,罗晓琳,柴志平(1)峰形模拟在纳秒强激光电离碘甲烷团簇质谱中离子来源分析的应用…………………………………………………………………………温丽华,李海洋,牛冬梅,罗晓琳,柴志平(6)人工神经网络用于FTMS准确质量的测定………………………………苏越,王昊阳,郭寅龙,相秉仁,安登魁(11)卷柏中挥发性组分的酶提取及气相色谱-质谱分析……………回瑞华,侯冬岩,刘晓媛,郭华,李学成,耿红苓(17)苯环壬酯及其代谢物的电子轰击和电喷雾电离质谱分析…     

新型飞行时间质谱离子移除装置的研制

本文介绍了一种用于飞行时间质谱离子检测器选择性移除非目标检测离子的脉冲电场装置。通过调节脉冲电压时序、优化脉冲电压值,实现对非目标检测离子的有效移除,使离子选择性地进入离子检测器,减少离子检测器的消耗,延长其使用寿命。结果表明,除了由脉冲上升沿和下降沿引起的质谱信号振荡对相邻飞行时间区域内的离子产生一定的影响外,该装置和方法可以选择性地、有效地移除非目标检测离子,以减少MCP离子检测器的消耗,延长其使用寿命,为飞行时间质谱非目标离子的移除提供一种简单、可行的方法。     

咪唑类物质的气溶胶飞行时间质谱研究

使用气溶胶激光飞行时间质谱（AL-TOF MS）和基于同步辐射光源的热解吸/可调谐真空紫外飞行时间光电离气溶胶质谱（TD-VUV-TOF-PIA MS）对7种咪唑类物质（咪唑、咪唑-2-甲醛、2-甲基咪唑、4-甲基咪唑、1-乙基咪唑、2-乙基咪唑、1-正丁基咪唑）进行分析，获得了每种样品在2种不同电离方式下的指纹图谱。前者主要获得这些样品物质的碎片峰信息，后者则主要获得含有完整母体峰的质谱信息。用上述标准样品的指纹图谱对乙二醛-硫酸铵溶液喷雾产生二次有机气溶胶（SOA）的质谱进行识别。通过咪唑样品的AL-TOF MS特征峰组合，可以解析出乙二醛与硫酸铵经水相反应生成咪唑类物质。由TD-VUV-TOF-PIA MS获得的咪唑样品在不同光子能量下的质谱特征，可以确认上述水相反应生成的咪唑类物质中含有咪唑与咪唑-2-甲醛。这两种方法互为补充，可为准确评估SOA水相形成贡献，以及完善气溶胶模式模拟提供数据支持。     

飞行时间质谱和高性能电子学控制技术

飞行时间质量分离器是飞行时间质谱仪的主要组成部分。飞行时间质谱（TOF MS）具有分析质量范围宽、分析速度快、仪器结构简单等优点，但离子初始动能和初始位置容易分散是影响其分辨率的核心因素。本综述根据本课题组多年的研制经验，着重介绍离子束垂直引入方式的反射式有栅网飞行时间质谱的离子光学以及相关电子学控制的核心技术原理。离子光学核心技术涉及到离子加速场和离子反射场的机械加工控制和精密装配控制等，电子学控制核心技术主要包括高压电源和高压脉冲电源的精密制作。     

高能量离子束诊断质谱仪的研制及性能表征

本研究开发了一台应用于高能量离子束诊断的直线式飞行时间质谱仪，实现了其与高能真空弧放电离子源的联用。该仪器加速电压30 kV，飞行腔有效飞行距离1.5 m，通过短脉冲离子门精确截取，ICCD高速相机优化聚焦，仪器分辨率优于90 FWHM，对放电过程中产生的等离子体可实现不同时间的离子成分分析。将该方法用于真空弧放电离子源放电过程中离子成分的检测，放电2 μs时，电离成分以气态离子C⁺、O⁺、C²⁺、O²⁺为主；放电6 μs后，除气体成分外，还可以检测到Fe⁺、Cu⁺及其同位素金属离子峰。该仪器能够给出离子源放电产生离子的种类、价态以及相对含量等信息，可实现整个放电过程产生离子成分信息的准确诊断。     

基于电喷雾电离源质谱仪系统的八电极线性离子阱性能研究

八电极线性离子阱在前期的理论模拟研究中取得了较好的质量分析性能,为验证理论模拟结果,选择其中最优的结构参数,设计、加工并组装了八电极线性离子阱实物,以此为基础搭建电喷雾电离源质谱测试系统。在传统射频电压施加模式下,测试八电极线性离子阱的分析性能。当扫描速度为765 u/s时,八电极线性离子阱获得离子峰的半峰宽可达0.3 u,对应利血平（m/z 609）的质量分辨率为2 030。当分析浓度为10 mg/m3的利血平样品时,对应的质谱峰信噪比可达45.8。本文进一步研究了扫描速度对质量分辨率和灵敏度的影响,实现了离子碰撞诱导解离,分析了不同浓度的25羟基维生素D2标准样品,线性动态范围可达4个数量级。结果表明,八电极线性离子阱具有良好的分析性能,可为结构简化线性离子阱的研究提供全新思路,推动小型化离子阱质谱仪的研究进展。     

谱图准确度在高分辨飞行时间质谱分析有机炸药中的应用

应用实时直接分析-高分辨飞行时间质谱（DART-TOF MS）对2,4,6-三硝基甲苯（TNT）、环三亚甲基三硝铵（RDX）、环四亚甲基四硝铵（HMX）、季戊四醇四硝酸酯（PETN）四种常见的有机炸药进行精确质量质谱解析,结果表明,即使在高质量精度的质谱上也不能获得化合物唯一的分子式。借助MassWorks软件对飞行时间质谱数据进行噪音过滤及峰形校正处理,可大大改善高分辨飞行时间质谱对目标化合物分子式识别的准确度,提高定性的准确性,为高分辨质谱解析未知化合物提供参考     

车载生物气溶胶质谱仪用小型化双极质量分析器的设计

生物气溶胶是大气中一类特殊的气溶胶，实时检测与识别生物气溶胶是实现生物预警预报的前提。小型车载生物气溶胶质谱仪对双极飞行时间(TOF)质量分析器的设计提出了要求。本研究基于指数脉冲延时引出技术开展小型TOF设计，结合SIMION 2020软件，模拟了速度分散为峰值800 m/s的高斯分布，空间分散0.3 mm情况下的粒子飞行轨迹。采用粒子群优化算法(PSO)自动优化TOF多组电极电压以及延迟时间。在130 ns延迟时间下，即使是极限的空间分散和能量分散也能实现全质量范围内的分辨率超过500,不同颗粒之间的质量偏差可控制在0.4 u以内。对比模拟分析了方波脉冲延时引出和指数脉冲延时引出对单个颗粒形成离子的分辨率影响，结果表明，指数脉冲延时引出在全质量范围内的分辨率显著优于方波脉冲。实验模拟了在颗粒处于光斑中心以及光斑偏左和偏右0.15 mm的极限情况下，颗粒电离位置对质谱分辨率的影响，结果表明，分辨率存在差异，但仍优于500。通过实际检测黑炭颗粒，小型TOF在全质量范围内可获得500以上的分辨率，能够满足车载生物气溶胶质谱仪的分辨率要求。虽然小型TOF的飞行长度为SPAMS 0525的6...     

Effect of non-uniform electron energy distribution function on plasma production in large arc driven negative ion source

Spatially non-uniform electron energy distribution function (EEDF) in an arc driven negative ion source (JAEA 10A negative ion source: 10 A NIS) is calculated numerically by a three-dimensional Monte Carlo kinetic model for electrons to understand spatial distribution of plasma production (such as atomic and ionic hydrogen (H(0)∕H(+)) production) in source chamber. The local EEDFs were directly calculated from electron orbits including electromagnetic effects and elastic∕inelastic collision forces. From the EEDF, spatial distributions of H(0)∕H(+) production rate were obtained. The results suggest that spatial non-uniformity of H(0)∕H(+) productions is enhanced by high energy component of EEDF.     

The shape of field emitters and the ion trajectories in three-dimensional atom probes

The lateral resolution of three-dimensional atom probes is mainly controlled by the aberrations of the ion trajectories near the specimen surface. For the first time, a simulation program has been developed to reconstruct the ion trajectories near a sharp hemispherical electrode defined at the atomic scale. Surface atoms submitted to the highest field were removed one by one. The consecutive gradual change of the surface topology was taken into account in the calculation of ion trajectories. As the tip was 'field evaporated', the initial spherical shape of the emitter was observed to transform gradually into a polygonal shape. When the tip reached its equilibrium shape, the field distribution at the tip surface was found to be much more uniform compared to the initial distribution. The calculated distribution of ion impacts on the detector exhibits the presence of depleted zones both at the centre of low index poles and along <001> zone axes. These predictions are in excellent agreement with experiments.     

Measurement of turbulent diffusion field behind a line heat source in a homogeneous shear flow

Turbulent diffusion behind a line heat source immersed in a nearly homogeneous shear flow is investigated. Test section of the wind tunnel is divided into 15 equal width channels equipped with adjustable internal flow resistances for the production of homogeneous shear flow. A combination of X-type hot wire for the measurement of velocity fluctuations and a cold wire for the measurement of temperature fluctuations has been devised to simultaneously obtain the cross correlations between the velocity and temperature fluctuations. The results show that all the distributions of velocity and scalar field are shifted toward the low velocity region of the homogeneous shear flow. The integral scales for velocity and scalar are different from each other in the shape of profiles so that the time scale ratio R does not remain constant. And the distributions of mean and fluctuating temperatures collapsed into a Gaussian curve by normalizing with mean half width and peak temperature.     

Distribution curves of sectional areas through some families of convex particles

We outline the results of a computer program which calculates frequency distributions of functions of cross-sectional regions of convex planar-faced polyhedra, ‘sphero-polyhedra’, and populations of perturbed polyhedra. This is done by ‘cutting’ a computer representation of the figure by a large number of random planes. The procedure is applied to cubes, dodecahedra, truncated octahedra, and approximate β-tetrakaidecahedra. Certain aspects of the shape of the object, e.g. sharpness of corners, angularity, compactness, and degree of symmetry are related to aspects of the shape of the distribution curves, e.g. beginning and ending points of the curves, rate of rise of the peak, relative location of the peak, and height and width of the peak.     

采样点分布对基于面形斜率径向基模型的自由曲面拟合精度的影响

鉴于自由曲面模型的面形拟合精度在自由曲面表征以及面形初始结构选取等研究中的重要性,本文针对基于面形斜率的高斯径向基表征模型,研究了不同的采样点分布类型对该模型面形拟合精度的影响。采用不同采样点分布拟合离轴二次曲面和带凸起的抛物面,结果表明采用均匀随机分布的采样点有利于实现高精度的面形拟合,且达到一定的拟合精度后,采样点的数目对拟合精度的影响有限。以离轴三反系统为设计实例,对比了由不同采样方式生成初始面形后系统的像质优化结果。结果显示,采用均匀随机型采样方式得到的初始面形进行系统优化,最终全视场平均调制传递函数(MTF)可以达到0.72以上,远高于由边缘集中采样方式生成初始面形后系统像质的优化结果,从而印证了理论研究结果。     

Reynolds number effect on turbulent secondary flow in a duct

Numerical simulations of fully-developed turbulent flow through a straight square duct at three Reynolds numbers of 190, 300, and 550 based on the friction velocity averaged over the duct perimeter and duct half width are reported. The effect of Reynolds number on the mean and turbulence statistics and secondary flow is investigated. The mean streamwise-velocity profiles along the wall bisector are found to obey a logarithmic scaling when they are normalized by the friction velocity at the mid-wall. Magnitudes and spatial distributions of the peak production and diffusion terms in the mean streamwise-vorticity equation normalized by the wall units are found to be unaffected by the Reynolds-number variation when they are considered in wall-unit coordinates.     

Matrix based algorithm for ion-beam figuring of optical elements

An algorithm for solving the problem of local shape errors of optical surfaces correcting by a small-sized ion beam, based on the matrix representation is presented. The algorithm involves searching for points that rise relative to the average height on the surface, where exposure to an ion beam of a given shape will lead to a decrease in the RMS deviation of the surface shape from the calculated one. It is shown that the new approach makes it possible to significantly expand the range of spatial frequencies, in which the height of relief can be reduced using the given ion beam size, and provides better results than the method of minimizing the functional of convolution of the ion beam and the surface map. Moreover, the new approach does not lead to appearance of shape errors (concentric structure) defined by the ion beam size and scanning step. An experiment for minimizing of local surface shape errors based on an etching map calculated using new approach was done. Matrix algorithm allowed in one procedure to reduce surface shape errors for a concave spherical optical element made of fused silica with a diameter D = 100 mm and a radius of curvature R = −137.5 mm in the RMS by more than 3 times. The initial RMS was 4.5 nm, RMS after treatment is 1.36 nm.     

供暖系统混水离心泵叶轮正反问题计算

基于流线迭代法和逐点积分法,用Fortran语言编程实现了供暖系统混水离心泵叶轮的水力设计,讨论了轴面流道形状、叶轮包角和滑移系数对设计计算结果的影响.基于Navier-Stokes方程,在贴体坐标系中,采用交错网格技术和SIMPLEC算法,对依据不同设计参数设计出的两个叶轮内部流场进行了数值模拟,并将计算得到的流场压力分布和轴面速度分布进行了对比,同时对两个叶轮进行性能预估.研究表明:轴面流道形状和叶轮包角影响叶轮内部压力场和速度场的均匀性,导致两个叶轮的水力效率值存在约2%的差别.     

Gas discharge ion source. I. Duoplasmatron

The effects of the plasma expansion cup on the operation of a duoplasmatron ion source have been investigated by measuring the total ion current and the distributions of the ion energy, mass, and current density. A copper expansion cup did not affect the magnetic field near the anode of the ion source and consequently the ion current density distribution was sharply peaked near the center of the cup. Ion energy distributions were approximately symmetrical about anode potential. The dominant ionic species were D(+) (3) and D(+) at low and high arc currents, respectively. Changes in the electrical potential of the copper cup with respect to the anode produced negligible changes in the above data. A mild steel plasma expansion cup caused the magnetic field to diverge and intercept the cup walls, resulting in ion current density distributions that were flatter and more amenable to focusing than the ones with the copper cup. With the steel cup at anode potential, the ion mass distribution was similar to that from the copper cup; however, the ion energy distribution was asymmetrical about the anode potential with a peak about 10-20 V above anode potential. The total ion current from this mode of operation was about one-third the value from the copper cup. If the steel cup assumed floating potential, about 50 V below anode potential, the total current increased to the level observed from the copper cup and the ion energy distribution was similar to that observed with the copper cup but the current density distribution was much flatter than that of the copper cup. The ion mass distribution was 60%-70% atomic ions over the entire arc current range investigated. Based on these data, a modified plasma expansion cup was designed with tapered steel walls lined with a boron nitride insert. The overall performance of the duoplasmatron ion source with this cup was superior to any of the previous three modes of operation. The improved design uses a molybdenum anode insert which is far superior to copper in regard to erosion over extended operating times. A total beam current of 200 mA was produced at an arc current of 24 A.