我们感谢罗伯特 · 伯杰 （菲利普斯大学马尔堡，德国） 一般激励讨论我们的数据和分子手性的解释。我们对于感谢茱莉亚凯德罗夫斯基、 亚历山大 Schießer 和 Michael Reggelin 从土达姆施塔特 （德国），以及本杰明 Spenger、 曼纽尔 · 马泽瑙尔 Jürgen Stohner 从 ZHAW Wädenswil （瑞士） 提供样品。
Hessen 国家倡议科学和卓越的经济成长，焦点 ELCH （电子系统动力学的手性） 和联邦教育部及研究 (BMBF) 下支持该项目。MS 由阿道夫 · 梅塞尔基金会承认金融支持。

注意: 请务必要熟悉所有可能危害连接与实验和实验室。下面的过程包括第四类激光器、 高电压和真空。物种要追究咨询材料安全数据表 (MSDS)。
 1。 制备 <ol><li>筹备考虑 注: 实际的实验开始前，两个主要选择必须作出; 第一次在调查可能的物种和第二在光谱仪电场。这里假定安装了以前使用其他实验和光谱仪本身不会因此而重新塑造。
	<ol><li><ol><li>样品的选择可望碎裂的示例进行签名的惯用手或结构特征进行调查。请牢记，氢原子常常被释放作为中性碎片;可能不能区分只是氢原子的数量不同的官能团。开始与简单 （也许非手性） 的物种，如应用或 haloethanes.</li>
			<li>检查样品，至少 0.02 mol 是可用的因为这是用在实验中获得成功的最小数额为止</li>
			<li>验证足够的蒸汽压力是可以实现的示例。根据该装置的设计，蒸汽压 &#62; 5 自置居所津贴是足够的射流密度激光实验的必要条件。如果蒸气压是明显降低，检查如果可以通过加热样品达到所需的蒸汽压力。这可能为液体和固体样品，由于后者的升华。如果加热是必需的它是需要有积极的温度梯度，沿路径的气体输送系统 （与喷嘴的最热门的组成部分） 为了避免凝结。更先进的样品制备计划像可能考虑由承运人气回升。</li>
		</ol></li> <li>光谱仪中的电场强度的选择 注: 50 到 100 V/cm 值被证明合理的库仑爆炸影像。最佳值，然而，取决于分光计的几何形状。以下步骤显示如何优化的电场强度。
		<ol><li>估计预期的阳离子碎片的飞行时间。如果光谱仪仅包含与长度 s 和电场强度 E 的均匀场区域，颗粒的质量 m 和电荷 q 的飞行平均时间只是给出 < img alt ="方程 1"src ="/files/ftp_upload/56062/56062eq1.jpg"/ ></li> <li>利用飞行时间 t 以上计算和公式估计传播 x 的片段阳离子与质量为 m 的探测器 < img alt ="方程 2"src ="/files/ftp_upload/56062/56062eq2.jpg"/ > 离子将获得动量 p x 的势头 （质子到 150 的原子单位） 达 400 原子单位。</li>
			<li>如果轻离子物种空间传播 x 大于探测器半径，增加电场强度计算中的，直到蔓延是几毫米比探测器尺寸小得多。电场强度不应该因为这会导致较低的分辨率为重碎片散布出来少在探测器上的高很多。</li>
		</ol></li></ol></li> <li>的实验装置检查 注: 实际测量之前，它已经要检查实验装置有充分的准备。
	<ol><li>互动室真空度的检查 &#60; 1 × 10 -9 自置居所津贴。如果这不是个案，残余气体将导致高背景率。如有疑问关于真空的条件，继续直到步骤 2.2.1 其残余气体的电离率确定。如果压力太高，执行泄漏检查。如果没有泄漏是明显的放入烤箱，分庭几天。</li>
		<li>验证的连接电源电压和探测器信号根据手册或实验描述。</li>
		<li>检查测量计算机上的数据采集软件是能够记录和分析至少四个离子。请确保死区时间的电子模块和信号的脉冲宽度小于 30 ns。</li>
	</ol></li> <li>准备样品交货 <ol><li>验证样品交货管是清洁和连接收紧。如果样品是腐蚀 （例如 酸性） 确保交付系统和粗加工泵的真空室中的所有组件都是调查对象的选取与兼容。粗加工的泵泵样本交付系统，打开阀门和验证实验的腔内的压力不会增加。</li>
		<li>清洁和准备样品收件人。用丙酮或通常实验室玻璃器皿清洗机超声波浴是充足的。</li>
		<li>编写储层和样品交货系统的加热如果样品需要加热 （参看 1.1.1.3）。最方便的方式是使用可调加热电路，加热丝、 温度传感器和温度控制器组成的每一个。</li>
		<li>如果样品具有很低的蒸汽压，或者如果它趋于形式集群 （例如 酸），接机或 copropagation 与惰性气体使用不同的方法。修改的设计，根据这些要求的气行。</li>
		<li>检查分子射流相一致。为此目的，使用稀有气体样品 （如 氩气） 从而达到密集射流 （大约 1 酒吧绝对压力应该足够为 50 微米的喷嘴）。通过移动的机械手的喷嘴安装最大化在射流转储部分压力。</li>
	</ol></li> <li>提供飞秒激光脉冲 注: 电离脉冲系统提供的飞秒激光。描述这种激光和其详细的使用已经超出本议定书的范围。如果使用了一种商业激光系统，请参考手册。
	<ol><li>上的激光开关并检查激光束的输出配置文件。</li>
		<li>检查和纠正 （如果必要） 通过调整各自的镜子实验的入口窗口的光束路径。</li>
		<li>如果有必要，用各自的机械手对齐试验室内的聚焦镜。中心对入射光束的聚焦镜反射。</li>
		<li>插入过滤器或旋转偏光器梁路径中的，以达到大约 6 x 10 14 W/厘米 2 峰值强度。对于正常库仑爆炸成像，使用线性极化。如果要追究二向色性的影响，通过四分之一波片，只是之前入口窗口更改偏振。</li>
		<li>在一个地方，它可以在其中记录的激光脉冲 （例如 一反射或传输通过对准镜） 的可靠副本插入一个光电二极管。光电二极管的输出连接到一台示波器和验证二极管产生清洁激光重复频率脉冲。</li>
		<li>总是阻止在不使用时梁。</li>
	</ol></li></ol> 2。拐弯处光谱仪和探测器 注: 议定书 》 的这一部分略取决于光谱仪和探测器系统的实际实现。描述在这里是有效的标准的 COLTRIMS 设置与六角延迟线探测器 (HEX75)。 10 在此实现中，探测器具有 7 输出通道: 一个用于微通道板(MCPs)，两个用于每个三层的阳极。
<ol><li>电源打开。
	<ol><li>关掉在互动室真空计，因为他们可能会产生离子探测器被视为。</li>
		<li>连接被放大的信号输出 (使用一种快速的放大器放大 &#8776; 100) 的快速 （最好是） 通用示波器对 MCP。将示波器设置为每个部分在时间尺度上的 5 或 10 ns 和 100 mV 每司在信号范围内。验证电子噪声小于 30 mV。</li>
		对高电压 <li>开关电源检测器。典型的离子化检测器，电压为-2,000 V 的前面板和 300 V 为阳极侧。电压取决于年龄的枇杷和应设置这样的模拟信号是最大，但不是饱和。检查当前。它取决于在探测器枇杷的抵抗，但不是应超过 50 µ A。在示波器的踪影，几个信号每秒几个几百毫伏信号高度应可见 (&#39; 暗计数 &#39;)。</li>
		<li>调到价值建立在步 1.1.2 光谱仪的电力供应。</li>
	</ol></li> <li>检查通过的残余气体电离探测器信号 注: 探测器启动的详细的说明，也可以见于各自手册。 11 ， 12 <ol><li>衰减激光强度对估计值低于 10 14 W/厘米 2 的重点。解除阻止激光和观看示波器跟踪。如果这导致率超过 5%的激光重复频率，在会议厅的残余气体量太高或激光束触动光谱仪。在继续之前解决此问题。如果计数率显著低于激光重复频率的 5%，逐步增加激光强度。</li>
		<li>有仔细看看信号。他们应该只显示一个峰几个几百个 mV 和 no &#39; 响 &#39; （后实际脉冲振荡）。MCP 信号的宽度应不超过 10 ns (FWHM)。</li>
		<li>看看所有六个阳极信号示波器记录。信号是更广泛这里 (20-30 ns)，和通常在电压要低一些。再次检查无干扰信号存在。如果所有的阳极信号低于 100 mV，增加电压 （步骤 2.1.3） 的步骤，50 诉调谐放大器的增益能够得到相同的脉冲高度为所有通道。</li>
		<li>通过恒比鉴频器 (CFD) 将这些模拟信号转换为标准的-0.8 V 的尼姆信号 （核仪表模块）。检查每个实验运行前 CFD 的设置。详细的说明，请参阅手册在因特网上。 12 送入尼姆脉冲时间数字转换器 (TDC)，用于记录与高分辨率 (通常 25 ps) 脉冲的到达时间。这些时间信号的数据采集和分析软件的输入。</li>
		<li>打开数据采集软件和数据记录的开始。看起来在每个通道-命中分布直方图应该是类似所有通道。如果那不是这样的一些渠道，检查这些渠道的 CFD 设置 （步骤 2.2.4）。检查通过另外检查信号总和设置运行时间每个探测器层探测器手册中所述。如有必要，更正的差价合约设置。</li>
		<li>显示探测器图像中的数据采集软件。探测器应显示为带有弥漫现场 （激光焦点图像） 在中心的圆圈。点的扩展主要是获取电离的残余气体的热速度。</li>
		<li>将信号馈入的激光二极管 （步骤 1.5.5） 的数据采集、 最好是探测器信号的方式相同。在软件中显示飞行时间谱。通过计算其预期的时间-的-航班从光谱仪几何 （步骤 1.1.2.1） 相关观测的峰残余气体种类 （H 2、 H 2 O，可能 N 2、 O 2、 CO 2）。</li>
		<li>试图通过计数率，使用激光系统的色散修正最大化最小化的激光脉冲持续时间。短脉冲 （和更高的峰值强度） 将导致率显著上升。</li>
		<li>如果背景压力是如此之低，收费不是足够高，以执行上述步骤，打开燃气射流 （见步骤 2.3），然后执行步骤 2.2.1 直到 2.2.8。飞行时间谱的步 2.2.7 然后显然非主导的射流中物种。</li>
		<li>发现了探测器的绝对方向。为了做到这一点，移动聚焦镜，使激光焦点图像移明显在探测器图像软件中。请注意 （用于步 5.1.1） 移动的方向。此步骤很重要测量的绝对构型的因为它能够避免测量动量的真实实验室空间反演.</li>
	</ol></li> <li>发现的气体射流和激光重叠。
	<ol><li>打开气体射流 1.3.5 步骤中所述。</li>
		<li>如果率增加和一个非常狭窄的地方 (&#39; 射流现货 &#39;) 可见探测器图像数据采集程序，在确保分子喷墨和激光束重叠的至少部分。在这种情况下，调整机械手的聚焦镜仔细地最大限度地在射流点计数。在最优重叠，他们应超过数从残余气体 （步骤 2.2） 的数量级。它可能需要减少激光强度，因为 MCP 计数率不应超过 30 千赫。如果由于残余气体电离背景太高比的信号从气体射流，考虑扩展激光束来达到一个更窄的重点在会议厅外。</li>
		<li>如果没有喷点在探测器图像上可见，调整机械手的聚焦镜在大步骤查找重叠在一起，并继续然后步 2.3.2。</li>
	</ol></li></ol> 3。样品交期 <ol><li>准备好所有的工具、 收件人垫圈和其他必需品，如样品暴露于环境应该最小化。</li>
	<li>填充到收件人将连接到实验的样本。如果样品具有很高的蒸气压力，冷却收件人和事先来样来减少蒸发损失，在这一步。</li>
	<li>将样品缸连接到喷射系统，并拧紧连接真空证明。冷却钢瓶 （以避免样品损失） 和几秒钟，以排除空气泵。</li>
	<li>阀门开启到喷嘴。在源湛压力误码率应增加到至少几个 10 -5 hPa。</li>
	<li>验证喷射点是可见的 （步骤 2.3.2） 和识别中飞行时间谱的最突出峰。</li>
	<li>优化实验条件 (调整温度、 激光强度的所涉及气体压力 &#8230;)，最大限度地从样品的电离速率。请记住，加热，导致组件的热膨胀系数，喷射机械手 （步骤 1.4.5） 调整可能是必要。</li>
</ol> 4。测量 注: 数据采集软件中执行以下步骤。
<ol><li>检查质谱和巧合谱。
	<ol><li>飞行时间频谱图并将不同的山峰分配给群众，可以发生在碎片 （父大规模、 丰富的片段）。</li>
		<li>绘制在 x 轴上的第一个离子的飞行时间和 y 轴上的第二个离子的飞行时间。以多项罪名的区域指示在巧合中发出的两个片段。锋利的对角线表明分手成两个带电碎片。</li>
		<li>情节类似的直方图的更多的粒子，例如 总和的航班时间为 x 轴上的第一次两个离子和为 y 轴上的第三和第四次离子飞行时间的总和。示例这种 multicoincidence 的频谱如 图 2 所示。</li>
		<li>尝试识别四粒子或五粒子谱不同的分手并检查是否有可能产下调查的结构信息的分手。</li>
	</ol></li> <li>估计测量时间。
	<ol><li>让实验运行约 1 小时，并检查计数为所选的通道数目。小心不要把背景事件。</li>
		<li>乘以这个数目与实验的预期时间。总人数中的相关渠道的计数应该至少几千。</li>
		<li>如果在所选的通道计数数目远远低于这个数字，增加激光强度并重复步骤 4.2.1 和 4.2.2。要小心的是仍然足够低，重合检测率 （见导言）。</li>
	</ol></li></ol> 5。数据分析 注: 库仑爆炸成像实验的数据分析是一种复杂但奖励任务因为很多参数可以微调后实验和大量的实测值的相关性可以探索动量。实验数据分析软件中后通常执行所有以下步骤。
<ol><li>校准实验参数 注: 在第一步，确保重建从探测器的位置和时间信息是正确的。类似于调整电子 （步骤 2.2） 的确切过程取决于特定的实现，在这种情况下数据分析软件。因此，可以考虑只一些一般性的建议。
	<ol><li>情节图像的探测器。检查所有三个阳极层，探测器图像的大小对应于 MCP 的实际大小和探测器图像的中心在 0。验证所有的三层组合产量相同的探测器图像。如果必要的旋转或翻转的检测器，这样的实验室帧对应探测器图像的坐标系统 （使用的测量步骤 2.2.10）。</li>
		<li>确定不同群众在飞行时间谱和适合分光计功能 （步骤 1.1.2.1） 为这些值。在此步骤中的重要参数是飞行时间偏移量 t 0，所有飞行时间值都必须更正的干</li>
		<li>看一看 （参见步骤 4.1.4） 的巧合谱和识别有前途分手渠道。建议一门放几个 100 的飞行时间值 ns 周围的有趣模式和只选择这些为进一步采取的步骤的窗口内的事件。否则为不必要的事件的量太大，会慢下来分析。</li>
		<li>存储 x、 y、 t 为进一步分析的修正的值。</li>
	</ol></li> <li>计算离子动量和能量。
	<ol><li>使用的实验参数和假设的大众收费比率，计算的动力组件 p x，p y 和 p z。使用这些计算动能的片段和他们的总和，动能释放 (KER)。</li>
		<li>使用巧合谱 （步骤 4.1.4） 用于微调电场强度 E 和光谱仪长度 s 和情节与飞行时间影响位置来确定 的位置偏移量 x 0 和 y 0 和速度 v j et 气体射流。如果精度标定是必要的使用 N 2 和分裂成两个单独的 O 2 控物种非常狭窄，好特征振动级数在动能释放 （见参考文献 13 和引用其中）。
		<ol><li>绘制 p x vs p y 等，并调整参数，以便动量分布在动量空间 （例如，关于在二维图形中的圆圈） 的球面上，以 0 为中心。这是，动能不应依赖离子片段的发射方向。</li>
			<li>绘制所有碎片从分子分手总和的势头。对于完整的分手，分布应窄 (通常 &#60; 10 原子单元动量) 和中心在 0.</li>
		</ol></li></ol></li> <li>选择相关的事件和探讨分子体系的性质。
	<ol><li>从背景分离实际的分手事件，通过设置约束在周围观察峰 （通常少于 20 原子单位在每个方向） 的总和势头。</li>
		<li>对于这些事件，使用矢量算法来构造包含结构信息，以进行调查的数量。下面一节中给出了实例为左和右旋异构体之间的区别。</li>
	</ol>
	</li>
</ol>

<ol>
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H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+the+Absolute+Configuration+of+a+Chiral+Epoxide+in+the+Gas+Phase.">Imaging the Absolute Configuration of a Chiral Epoxide in the Gas Phase.</a> Science. 342 (6162), 1084-1186 (2013).</li><li>D&#246;rner, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cold+Target+Recoil+Ion+Momentum+Spectroscopy:+a+'momentum+microscope'+to+view+atomic+collision+dynamics.">Cold Target Recoil Ion Momentum Spectroscopy: a 'momentum microscope' to view atomic collision dynamics.</a> Physics Reports. 330, 95-192 (2000).</li><li>Ullrich, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recoil-ion+and+electron+momentum+spectroscopy:+reaction-microscopes.">Recoil-ion and electron momentum spectroscopy: reaction-microscopes.</a> Rep. 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Phys. 66 (9), 1463-1545 (2003).</li><li>Jagutzki, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+Hit+Readout+of+a+Microchannel+Plate+Detector+With+a+Three-Layer+Delay-Line+Anode.">Multiple Hit Readout of a Microchannel Plate Detector With a Three-Layer Delay-Line Anode.</a> IEEE Trans Nucl Sci. 49 (5), 2477-2483 (2002).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> RoentDek GmbH MCP Delay Line Detector Manual. , (2017).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> RoentDek GmbH The RoentDek Constant Fraction Discriminators CFD8c, CFD7x, CFD4c, CFD1c and CFD1x. , (2017).</li><li>Zeller, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+the+He2+quantum+halo+state+using+a+free+electron+laser.">Imaging the He2 quantum halo state using a free electron laser.</a> PNAS. 113 (51), 14651-14655 (2016).</li><li>Pitzer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stereochemical+configuration+and+selective+excitation+of+the+chiral+molecule+halothane.">Stereochemical configuration and selective excitation of the chiral molecule halothane.</a> J. Phys. B.: At. Mol. Opt. Phys. 49 (23), 234001 (2016).</li><li>Hine, J., Dowell, A. M., Singley, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+Dihalides+as+Intermediates+in+the+Basic+Hydrolysis+of+Haloforms:+IV+Relative+Reactivities+of+Haloforms.">Carbon Dihalides as Intermediates in the Basic Hydrolysis of Haloforms: IV Relative Reactivities of Haloforms.</a> J. Am. Soc. Chem. 78, 479-482 (1956).</li><li>Wales, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+coincidence+detection+algorithm+for+improving+detection+rates+in+coulomb+explosion+imaging.">A coincidence detection algorithm for improving detection rates in coulomb explosion imaging.</a> Nucl. Instr. Meth. in Phys. Res. A. 667, 11-15 (2012).</li><li>Kastirke, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Konstruktion und Aufbau einer UHV-tauglichen COLTRIMS-Kammer. , (2014).</li><li>Calegari, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Charge+migration+induced+by+attosecond+pulses+in+bio-relevant+molecules.">Charge migration induced by attosecond pulses in bio-relevant molecules.</a> J. Phys. B.: At. Mol. Opt. Phys. 49 (14), 142001 (2016).</li><li>Gaie-Levrel, F., Garcia, G. 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作者宣称没有相互竞争的利益。

由于各种元器件，COLTRIMS 安装程序需要相当高水平的技术专长，尤其是在真空技术、 粒子检测、 快速的电子和数据分析等领域。在谈到复杂种类调查之前, 它应因此彻底检查如果运行安装程序的方法正确，例如通过执行和分析测量对双原子或原子的物种。
优化的强度和持续时间的激光脉冲与分子射流重叠实现尽可能多尽可能多个电离事件至关重要。随着动量分布可能?...

手性是性质的我们一直令人着迷的研究人员超过 150 年特征。在 19th世纪、 巴斯德、 范特霍夫和别人发现分子可以发生在并不是超级不再依赖-像我们的左手和右手的两个镜像结构。此属性被称为 '手'，从 '手' 的希腊语。
到目前为止，已发现了在热力学性质或左和右旋形式 （两个对映体'） 的能量水平无差异。分析了样品的惯用手，分离对映体，可以使用与其他手性分子相互作用，例如这样做的各种色谱方法。1 （振动） 圆二色性、 (V) CD、 旋光色散，ORD，Chiroptical 方法经常被雇用来区分对映体。2
微观结构测定的时候，这些技术需要附加信息，例如从量子化学计算。唯一的技术正在被广泛接受，直接确定的绝对构型是反常的 x 射线衍射。3
它最近被证明绝对构型的简单手性物种可以由库仑爆炸成像。4,5在这种方法，在气相中的分子是乘以电离，其余内核强烈排斥对方。这斥力导致的分子的快速瓦解 （' 爆炸'）。片段动量相关结构的分子 — — 小分子的大小和方向的动量方向对应出奇好债券轴。使用分子离子束从加速器，开创了分子结构测定的库仑爆炸。6这束箔技术最近也被应用于手性识别。7
与异常的 x 射线衍射、 样品不能结晶，但在气相中提供。这使得库仑爆炸方法挥发性化合物的理想和对 x-射线衍射从而补充。在某些情况下，甚至可以为单个分子已确定惯用手。
在实践中，分子的结构的精确重建已证明困难甚至甲烷衍生物，如中央碳与不同取代基的分子。这被归功于片段之间的相互作用不完全是库仑和并不是所有债券同时都打破。为了获得立体化学信息，尤其是以区分对映体，这种重建是幸运的是不必要的。相反，可以相关不同片段的动量向量，是明显的左和右旋分子的产量。为了得到可靠的结果，至少四个片段动量必须被记录下来。
为了衡量这势头信息，从一个 — — 且只有一个 — — 分子分手片段必须在一个单一的测量步骤中检测到。这种情况通常被称为 '重合检测'。此外，发射方向必须加以分析，这数额在实践中记录的时间和片段的位置影响在列表模式数据格式。
在原子和分子物理学中，技术已经采用静电光谱仪的大规模分离和时间和位置灵敏多命中探测器实现这种测量的方法。最突出的例子是 COLTRIMS （冷目标反冲离子动量谱仪） 设置 — — 也称为反应显微镜。8,9这种实验示意图图 1中给出。相反可以记录以及电子的标准 COLTRIMS，库仑爆炸成像要求只有离子化检测器。
光谱仪和探测器安装在超高真空条件下 (&#60; 1 × 10-9自置居所津贴) 以避免创建从残余气体离子。通过超音速规模扩张所造成的气态自由分子射流提供样品的单分子: 根据蒸汽压力，分子扩大通过小的喷嘴 （大约 50 µ m 直径） 放入真空。实验中，源分庭，这一部分被隔开相互作用区域通常两撇和差异泵浦的阶段。额外的差异抽水部分位于后面的互动区域转储气体射流，从而避免背景气体相互作用区域。
电离辐射与分子射流 90 ° 之下相交。大多数实验室现在用飞秒激光脉冲的同步辐射，快离子或电子冲击虽可能 '弹' 诱使库仑爆炸。
以下协议使重合的离子和飞秒激光成像的运行安装程序可在实验室中的假设。进四个或甚至五个片段诱导库仑爆炸所需的峰值强度必须大约 6 x 1014 W/厘米2。为了避免极长的测量，激光重复频率应 10 千赫或更多。这是关键的因为一方面，重合检测可以只确定如果碎片在激光焦点的概率远远低于 1 每激光脉冲 （理想情况下不超过 10%)。总的碎片率，另一方面，不应低于几千赫因为有关多重碎裂通路的份额通常是小于 10-4。同样令人鼓舞的事实，应该提到的是原则单一碎片事件已足以识别的光学纯样品，配置和检测几百允许确定的对映异构体中丰度未知的对映体组成的样品。

<table><tbody><tr><td>CHBrCl2</td><td>SigmaAldrich</td><td>139181-10G</td><td>or other suitable sample</td></tr><tr><td>femtosecond laser system</td><td>KMLabs</td><td>Wyvern500</td><td></td></tr><tr><td>High-reflective mirrors</td><td>EKSMA</td><td>042-0800</td><td></td></tr><tr><td>mirror mounts</td><td>Newport</td><td>U100-A-LH-2K&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>focusing mirror (protected silver, f = 75 mm)</td><td>Thorlabs&amp;nbsp;</td><td>CM254-075-P01</td><td>(if available: f = 60 mm)</td></tr><tr><td>COLTRIMS spectrometer, including electronics and data acquisition system</td><td>RoentDek</td><td>custom</td><td>contrary to the standard COLTRIMS, only one detector is needed</td></tr></tbody></table>

coulomb explosion imaging as a tool to distinguish between stereoisomers

这篇文章显示了如何使用 COLTRIMS （冷目标反冲离子动量谱仪） 或"反应显微镜"技术来区分对映体 （立体异构体） 的单个分子水平上的简单手性物种。在此方法中，样品的气体分子射流扩展进入真空室和飞秒 (fs) 激光脉冲与相交。高强度的脉冲会导致快速多个电离，点燃了所谓的库仑爆炸，产生几个阳离子 （正电） 片段。静电场指导这些阳离子时间和位置灵敏探测器上。类似于飞行时间质谱仪，每个离子的到达时间产生于它的质量信息。如有盈余，静电场被调整中，发射方向和动能后碎片导致变异在飞行时间和影响位置探测器的一种方式。
每个离子影响创建电子信号在探测器;这个信号是治疗高频率电子和计算机记录事件的事件。注册的数据对应的影响时间和位置。面对这些数据，可以计算能量和每个片段的发射方向。这些值是根据调查，即对债券长度和相对位置的原子，允许以确定分子通过分子的手性的简单手性物种和其他同分异构体的功能分子的结构性质有关。

在这一部分中，我们显示结果的应用。这些种类的原理验证实验由于其简单性和蒸汽压力高的理想选择。同时，利用同步辐射光源的软 x 射线光子诱导多个电离研究了更复杂的物种氟烷。14
CHBrClF
Bromochlorofluoromethane (CHBrClF) 是一个教科书例子为手性分子与手性碳原?...

Watch this Scientific Journal Video about Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers at JoVE.com

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

作为一种工具来区分立体异构体的库仑爆炸成像

小手性的物种，库仑爆炸成像提供了新的途径来确定单个分子的手性。

This article shows how the COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) or the "reaction microscope" technique can be used to distinguish ...

coulomb-explosion-imaging-as-tool-to-distinguish-between

Universidad de Cartagena UDEC

Education

Research

JoVE Core

JoVE Journal

Organic Chemistry

Chemistry

Unit 1

Transition Metals and Coordination Complexes

Stereoisomerism

SCIENTISTS IN ACTION

9.0K 次观看.  Goethe-Universität Frankfurt am Main. 小手性的物种，库仑爆炸成像提供了新的途径来确定单个分子的手性。

视频: Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

Spatial Separation of Molecular Conformers and Clusters

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold molecular beams. However, these beams often contain multiple conformers and clusters, even at low rotational temperatures. We present an experimental methodology that allows the spatial separation of these constituent parts of a molecular beam expansion. Using an electric deflector the beam is separated by its mass-to-dipole moment ratio, analogous to a bender or an electric sector mass spectrometer spatially dispersing charged molecules on the basis of their mass-to-charge ratio. This deflector exploits the Stark effect in an inhomogeneous electric field and allows the separation of individual species of polar neutral molecules and clusters. It furthermore allows the selection of the coldest part of a molecular beam, as low-energy rotational quantum states generally experience the largest deflection. Different structural isomers (conformers) of a species can be separated due to the different arrangement of functional groups, which leads to distinct dipole moments. These are exploited by the electrostatic deflector for the production of a conformationally pure sample from a molecular beam. Similarly, specific cluster stoichiometries can be selected, as the mass and dipole moment of a given cluster depends on the degree of solvation around the parent molecule. This allows experiments on specific cluster sizes and structures, enabling the systematic study of solvation of neutral molecules.

We present a technique that allows the spatial separation of different conformers or clusters present in a molecular beam. An electrostatic deflector is used to separate species by their mass-to-dipole moment ratio, leading to the production of gas-phase ensembles of a single conformer or cluster stoichiometry.

分子构象器和星团的空间分离

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold ...

科研

工程学

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomic molecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laser propagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput, 2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, the observed angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation. To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setup in which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, the pump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movie is sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existing standard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

We present a protocol for creating a real-time movie of a molecular rotational wave packet using a high-resolution Coulomb explosion imaging setup.

激光驱动的超快分子旋转直接成像

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb ...

化学

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F&#8722;

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F&#8722;), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.

Here, we present a protocol for photoelectron imaging of anionic species. Anions generated in vacuo and separated by mass spectrometry are probed using velocity mapped photoelectron imaging, providing details of anion and neutral energy levels, anion and neutral structure and the nature of the anion electronic state.

由 F− 310 Nm 支队所示的阴离子光电子成像

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound ...

Using a Cyclic Ion Mobility Spectrometer for Tandem Ion Mobility Experiments

Accurate characterization of chemical structures is important to understand their underlying biological mechanisms and functional properties. Mass spectrometry (MS) is a popular tool but is not always sufficient to completely unveil all structural features. For example, although carbohydrates are biologically relevant, their characterization is complicated by numerous levels of isomerism. Ion mobility spectrometry (IMS) is an interesting complement because it is sensitive to ion conformations and, thus, to isomerism. 
Furthermore, recent advances have significantly improved the technique: the last generation of Cyclic IMS instruments offers additional capabilities compared to linear IMS instruments, such as an increased resolving power or the possibility to perform tandem ion mobility (IMS/IMS) experiments. During IMS/IMS, an ion is selected based on its ion mobility, fragmented, and reanalyzed to obtain ion mobility information about its fragments. Recent work showed that the mobility profiles of the fragments contained in such IMS/IMS data can act as a fingerprint of a particular glycan and can be used in a molecular networking strategy to organize glycomics datasets in a structurally relevant way. 
The goal of this protocol is thus to describe how to generate IMS/IMS data, from sample preparation to the final Collision Cross Section (CCS) calibration of the ion mobility dimension that yields reproducible spectra. Taking the example of one representative glycan, this protocol will show how to build an IMS/IMS control sequence on a Cyclic IMS instrument, how to account for this control sequence to translate IMS arrival time into drift time (i.e., the effective separation time applied to the ions), and how to extract the relevant mobility information from the raw data. This protocol is designed to clearly explain the critical points of an IMS/IMS experiment and thus help new Cyclic IMS users perform straightforward and reproducible acquisitions.

Ion mobility spectrometry (IMS) is an interesting complement to mass spectrometry for the characterization of biomolecules, notably because it is sensitive to isomerism. This protocol describes a tandem IMS (IMS/IMS) experiment, which allows the isolation of a molecule and the generation of the mobility profiles of its fragments.

使用循环离子淌度光谱仪进行串联离子淌度实验

Accurate characterization of chemical structures is important to understand their underlying biological mechanisms and functional properties. Mass ...

Direct Comparison of Hyperspectral Stimulated Raman Scattering and Coherent Anti-Stokes Raman Scattering Microscopy for Chemical Imaging

Stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) microscopy are the most widely used coherent Raman scattering imaging technologies. Hyperspectral SRS and CARS imaging offer Raman spectral information at every pixel, which enables better separation of different chemical compositions. Although both techniques require two excitation lasers, their signal detection schemes and spectral properties are quite different. The goal of this protocol is to perform both hyperspectral SRS and CARS imaging on a single platform and compare the two microscopy techniques for imaging different biological samples. The spectral focusing method is employed to acquire spectral information using femtosecond lasers. By using standard chemical samples, the sensitivity, spatial resolution, and spectral resolution of SRS and CARS in the same excitation conditions (i.e., power at the sample, pixel dwell time, objective lens, pulse energy) are compared. The imaging contrasts of CARS and SRS for biological samples are juxtaposed and compared. The direct comparison of CARS and SRS performances would allow for optimal selection of the modality for chemical imaging.

This paper directly compares the resolution, sensitivity, and imaging contrasts of stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) integrated into the same microscope platform. The results show that CARS has a better spatial resolution, SRS gives better contrasts and spectral resolution, and both methods have similar sensitivity.

高光谱受激拉曼散射与相干反斯托克斯拉曼散射显微镜在化学成像中的应用的直接比较

Stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) microscopy are the most widely used coherent Raman scattering imaging ...

Differential Imaging of Biological Structures with Doubly-resonant Coherent Anti-stokes Raman Scattering (CARS)

Coherent Raman imaging techniques have seen a dramatic increase in activity over the past decade due to their promise to enable label-free optical imaging with high molecular specificity 1. The sensitivity of these techniques, however, is many orders of magnitude weaker than fluorescence, requiring milli-molar molecular concentrations 1,2. Here, we describe a technique that can enable the detection of weak or low concentrations of Raman-active molecules by amplifying their signal with that obtained from strong or abundant Raman scatterers. The interaction of short pulsed lasers in a biological sample generates a variety of coherent Raman scattering signals, each of which carry unique chemical information about the sample. Typically, only one of these signals, e.g. Coherent Anti-stokes Raman scattering (CARS), is used to generate an image while the others are discarded. However, when these other signals, including 3-color CARS and four-wave mixing (FWM), are collected and compared to the CARS signal, otherwise difficult to detect information can be extracted 3. For example, doubly-resonant CARS (DR-CARS) is the result of the constructive interference between two resonant signals 4. We demonstrate how tuning of the three lasers required to produce DR-CARS signals to the 2845 cm-1 CH stretch vibration in lipids and the 2120 cm-1 CD stretching vibration of a deuterated molecule (e.g. deuterated sugars, fatty acids, etc.) can be utilized to probe both Raman resonances simultaneously. Under these conditions, in addition to CARS signals from each resonance, a combined DR-CARS signal probing both is also generated. We demonstrate how detecting the difference between the DR-CARS signal and the amplifying signal from an abundant molecule's vibration can be used to enhance the sensitivity for the weaker signal. We further demonstrate that this approach even extends to applications where both signals are generated from different molecules, such that e.g. using the strong Raman signal of a solvent can enhance the weak Raman signal of a dilute solute.

Differential Imaging of Biological Structures with Doubly-resonant Coherent Anti-stokes Raman Scattering CARS

A combination of three single wavelength short-pulsed lasers is used to generate coherent anti-Stokes Raman scattering (CARS) and doubly-resonant CARS (DR-CARS). The difference between these signals provides enhanced sensitivity for otherwise difficult to detect coherent Raman signals, enabling imaging of weak Raman scatterers.

差分成像生物结构与双共振相干反斯托克斯拉曼散射（CARS）

Coherent Raman imaging techniques have seen a dramatic increase in activity over the past decade due to their promise to enable label-free optical imaging ...

生物学

使用 VSFG 显微镜进行多模式、快速、高光谱化学分析

Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy

Vibrational sum-frequency generation (VSFG), a second-order nonlinear optical signal, has traditionally been used to study molecules at interfaces as a spectroscopy technique with a spatial resolution of ~100 &#181;m. However, the spectroscopy is not sensitive to the heterogeneity of a sample. To study mesoscopically heterogeneous samples, we, along with others, pushed the resolution limit of VSFG spectroscopy down to ~1 &#181;m level and constructed the VSFG microscope. This imaging technique not only can resolve sample morphologies through imaging, but also record a broadband VSFG spectrum at every pixel of the images. Being a second-order nonlinear optical technique, its selection rule enables the visualization of non-centrosymmetric or chiral self-assembled structures commonly found in biology, materials science, and bioengineering, among others. In this article, the audience will be guided through an inverted transmission design that allows for imaging unfixed samples. This work also showcases that VSFG microscopy can resolve chemical-specific geometric information of individual self-assembled sheets by combining it with a neural network function solver. Lastly, the images obtained under brightfield, SHG, and VSFG configurations of various samples briefly discuss the unique information revealed by VSFG imaging.

作者聚焦:揭示 VSFG 显微镜在研究介观异质自组装结构中的潜力 

A multimodal, rapid hyperspectral imaging framework was developed to obtain broadband vibrational sum-frequency generation (VSFG) images, along with brightfield, second harmonic generation (SHG) imaging modalities. Due to the infrared frequency being resonant with molecular vibrations, microscopic structural and mesoscopic morphology knowledge is revealed of symmetry-allowed samples.

基于线扫描振动和频生成显微镜的多模态非线性高光谱化学成像

Vibrational sum-frequency generation (VSFG), a second-order nonlinear optical signal, has traditionally been used to study molecules at interfaces as a ...

Stereoisomers

On the basis of mirror symmetry, stereoisomers of an organic molecule can be further classified into diastereomers and enantiomers. Diastereomers are stereoisomers that are not mirror images of each other. Substituted alkenes, such as the cis and trans isomers of 2-butene, are diastereomers, as these molecules exhibit different spatial orientations of their constituent atoms, are not mirror images of each other,&#160;and do not interconvert. Here, the interconversion is suppressed due to restricted rotation around the &#960; bond. Another class of diastereomers &#8212; those without &#960; bonds &#8212; are molecules that have non-superposable spatial orientations and exhibit different configurations of their substituent groups at some, but not all, stereocenters. For example, cis-1,2-dimethylcyclohexane and trans-1,2-dimethylcyclohexane are diastereomers, as these molecules are not superposable and have a different configuration of the methyl and hydrogen groups at only one out of their two stereocenters.
Enantiomers are stereoisomers that are mirror images of each other. As only chiral molecules can have non-superposable mirror images, enantiomers are chiral molecules. For example, the chiral molecule 2-butanol and its mirror image are enantiomers, as these molecules exhibit non-superposable spatial orientations of their constituent atoms and are mirror images of each other. A chiral molecule and its mirror image are collectively referred to as an enantiomeric pair, or a pair of enantiomers. The enantiomer of a chiral molecule can be drawn by taking its mirror image from any position or&#160;exchanging the positions of two of the substituents at each stereocenter of the molecule.

Stereoisomers: Diastereomers and Enantiomers

立体异构体

On the basis of mirror symmetry, stereoisomers of an organic molecule can be further classified into diastereomers and enantiomers. Diastereomers are ...

作为一种工具来区分立体异构体的库仑爆炸成像

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分子构象器和星团的空间分离

激光驱动的超快分子旋转直接成像

由 F⁻ 310 Nm 支队所示的阴离子光电子成像

使用循环离子淌度光谱仪进行串联离子淌度实验

高光谱受激拉曼散射与相干反斯托克斯拉曼散射显微镜在化学成像中的应用的直接比较

差分成像生物结构与双共振相干反斯托克斯拉曼散射（CARS）

基于线扫描振动和频生成显微镜的多模态非线性高光谱化学成像

基于线扫描振动和频生成显微镜的多模态非线性高光谱化学成像

基于线扫描振动和频生成显微镜的多模态非线性高光谱化学成像

立体异构体