这项工作得到了美国陆军研究办公室的支持, 通过合同 W911NF-18-1-0051。

注: 所有商业获得的仪器和零件, 如激光, 真空泵, 室, 飞行时间管和微通道板检测器是根据制造商的说明或用户手册安装和操作。激光安全护目镜设计的操作激光强度和波长应佩戴。
1. 施工26毫秒
<ol><li>设计和建造一个超高真空 (特高压) 室, 有足够的空间容纳标准的离子光学26和规定安装在2¾ "法兰上的光学窗口的任何一侧的离子光学 (图 1)。</li>
	<li>将1米飞行管上安装的离子光学束连接到燃烧室。 注意: 为了节省光学表上的空间, 垂直安装离子光学和飞行管是最容易的。</li>
	<li>将1/16 不锈钢管插入萃取器和驱板之间的腔内, 将管子从腔体中取出, 并将其连接至¼ "不锈钢管27。将一个或多个可变泄漏阀附加到¼ "不锈钢管" 中。 注: 可将含有分子样品或气罐的玻璃管附着在取样入口的导管上。</li>
	<li>将18毫米微通道板栈安装在 Z 堆栈配置29上, 在飞行管的末端。</li>
	<li>将两个光学窗口 (1 毫米厚度, 50 毫米直径, 熔融二氧化硅) 安装在2¾ "法兰上的房间。 注: 激光束通过这两个窗口通过驱和萃取板之间的空间传播。</li>
	<li>通过电流贯穿件可和 BNC 电缆将离子光学和探测器连接到高压电源。</li>
	<li>将一涡轮分子泵连接到离子光学附近的腔室, 再将第二泵安装到探测器附近的飞行管末端 (图 1)。将两个泵连接到适当的后备泵。 注意: 当将涡轮分子泵连接到垂直安装的飞行管的末端时, 注意确保系统不会由于泵的重量而倾斜到一侧。通过将真空室连接到光学表, 可以减轻此问题。</li>
	<li>打开水泵, 等待24小时。室内压力应低于 10-8乇, 无样品。如果压力高, 检查泄漏和拧紧螺母或烘烤室, 直到达到预期的压力。</li>
</ol>2. 光学泵和探头路径的构建
注:图 1给出了泵和探头光学路径的示意图。
<ol><li>提供飞秒激光脉冲 注: 飞秒激光脉冲 (800 nm) 是由商业 Ti: 蓝宝石再生放大器源操作, 根据制造商的手册。<ol>
<li>打开激光, 等待约30分钟, 使其稳定。</li>
		<li>位置 90:10 (%R:%T) 光束分配器后, 激光输出产生两个副本, 这将用于构造泵和探头光束线。检查两个副本的激光功率, 以确保足够的电源交付。</li>
		<li>将反射光束定向到光参量放大器中, 并利用本手册中的程序对输出功率进行优化。</li>
	</ol>
</li>
	<li>泵浦光路的制备<ol>
<li>设置可选的软件以选择所需的波长。</li>
		<li>通过λ/2 波板 (WP) 和偏光片 (P) 直接将输出光束从通过。</li>
		<li>阻挡 p 偏振光束, 并将 s-偏振光束定向到凹 (f =-10 厘米) 和凸 (f = 50 厘米) 镜面, 以5的系数扩大其直径。</li>
		<li>将展开的光束定向到分色镜 (DC)。</li>
	</ol>
</li>
	<li>探针光路的制备<ol>
<li>将通过90:10 光束拆分器的光束定向到凸镜 (f = 20 厘米) 和凹镜 (f =-10 厘米), 以减小其直径 (以2为因子)。</li>
		<li>将向下准直光束定向到安装在机动线性延迟阶段的空心复古反射器。在复古反射镜前调整两个平面镜的安装旋钮, 以确保当舞台沿其完整的行程移动时, 后反光反射器的光束位置不会发生变化。 注意: 这可以确保泵探头的空间重叠将保持在整个扫描范围内。</li>
		<li>在延迟阶段后插入可调谐中性密度 (ND) 滤波器, 以减弱探头脉冲的功率, 在 ND 滤波器后插入虹膜以调整光束直径, 并将光束定向到分色镜 (DC)。</li>
	</ol>
</li>
	<li>泵和探头脉冲持续时间的测量 注: 泵和探头脉冲的持续时间用内置的第二谐波产生-频率分辨光门 (SHG) 设置来测量。关于 SHG 青蛙的设置, 测量过程和数据检索算法的构造的细节在别处被描述30,31,32。在我们的实验中, 输出的脉冲持续时间通常是大约 20 fs 和 800 nm 脉冲约 30 fs19,20,27。然而, OPAs 可以引入高阶脉冲畸变, 因此, 可能需要实现脉冲压缩, 例如, 啁啾镜像10,11,12,13或声光调制器16。<ol>
<li>堵塞泵或探头梁。把剩下的光束直接放到青蛙里, 用平镜放置在混合了泵和探针脉冲的分色镜之后。</li>
		<li>确保两束在β钡硼酸盐 (BBO) 晶体中的青蛙重叠。调整光束对准和延迟阶段, 直到第三束在两个原梁之间可见。</li>
		<li>用虹膜和f = 10 cm 透镜, 隔绝并且聚焦光束入连接到光谱仪和计算机的光纤装载。</li>
		<li>采集青蛙扫描, 用相应的软件和检索算法检索脉冲形状。</li>
		<li>重复步骤 2.4. 1-2. 4.3 为另一束。取下镜子, 把光束引向青蛙。</li>
	</ol>
</li>
	<li>泵与探头梁的粗空间重叠 注: 如果泵和探头光束可见, 则可以跳过步骤2.5.1。<ol>
<li>在分色后插入15毫米直径的 BBO 晶体, 双光束的波长加倍, 从而使它们可见。 注: 这是最容易使用的一个 1200-1300 nm 的激光测量波长, 使一个橙色 600-650 nm 光束, 很容易区分从蓝色 400 nm 探针光束。注意确保泵束最密集的区域通过晶体的中心。晶体的角度应该优化, 使橙色和蓝色的脉冲很容易看到, 虽然这个角度可能不对应的最大强度的给定颜色。</li>
		<li>调整泵和探头光束对齐, 使用前镜安装在分色, 使光束传播 collinearly 通过飞行-MS 室和从另一侧。 注: 探头光束直径较小, 应集中在泵梁的中间。</li>
	</ol>
</li>
	<li>泵与探头梁的粗糙时间重叠 注: 此处描述的方法仅限于示波器分辨率, 只能在延迟阶段的几毫米行程内确定零延迟位置。<ol>
<li>在泵和探头横梁的路径中, 将一个快速光电二极管探测器放在窗口入口前几厘米处。将探测器电缆连接到数字示波器, 并独立定位泵和探头脉冲的信号。</li>
		<li>调整机动延迟阶段在探头线上的位置, 这样在示波器中的泵和探头信号会被世俗地重叠。如果一个信号一直在前面 (后面) 的另一个在示波器, 移动装载持有机动延迟阶段, 以缩短或延长路径长度根据需要。</li>
		<li>卸下光电二极管探测器。</li>
	</ol>
</li>
</ol>3. 初步测量
注: 我们实验中的所有数据都是使用商用仪表控制软件 (材料表) 内部编写的代码获取的。所有仪器驱动软件都是从各自的制造商那里获得的。
<ol><li>泵浦脉冲绝对峰值强度的标定28<ol>
<li>阻挡探头光束, 在入口窗前直接插入f = 20 厘米透镜安装在一个手动的线性平移阶段。</li>
		<li>调整波形板 (WP) 旋转角度 (图 1), 以最大限度地提高泵浦光束在镜头前的功率。</li>
		<li>将一罐氙气气体连接到飞行通道-MS 室入口, 并调整泄漏阀控制气体流向燃烧室, 使压力表读数介于 5-10 x 10-8乇之间。在调整采样压力时, 要确保时间-MS 电源电压熄灭, 以避免由于压力峰值引起的 MCP 探测器损坏。</li>
		<li>将 MCP 探测器和激光信号延迟发生器的输出电缆连接到数字示波器。设置示波器触发激光信号。</li>
		<li>打开 "MS" 电源, 检查电压。v1、v2、v3和 v4 (图 2) 的电压的典型值分别为 +4,190 v、+3,910 v、0 v 和-3,000 v。</li>
		<li>在示波器中直接或通过连接到示波器的计算机检查氙+ (和较高电荷状态) 的离子信号。</li>
		<li>调整手持透镜的手动平移阶段的位置, 使总离子信号最大化。这一步确保泵束聚焦与图 2所示的0.5 毫米狭缝重叠。</li>
		<li>使用数据采集软件记录氙质量谱。</li>
		<li>通过旋转 WP 角度来降低激光功率, 获得比先前测量的功率低20兆瓦的功率。</li>
		<li>重复步骤 3.1. 8-3. 1.9, 直到激光功率过低, 产生可测量的氙+信号。应记录在不同激光功率下的10-15 质谱。</li>
		<li>使用适当的数据分析软件, 按照参考28中的步骤, 识别氙+ (1.12 x 1014 W cm-2)28的绝对饱和强度对应的激光脉冲能量。本程序为进一步实验中使用的任何泵浦脉冲能量提供绝对强度刻度。</li>
	</ol></li>
	<li>探针脉冲绝对峰值强度的标定33 注: 由于探头脉冲强度较弱, 无法使用步骤3.1 中描述的氙标定方法。相反, 实验中的探针强度可以通过用数码相机32, 以及脉冲持续时间和能量来测量焦距的光斑大小来估计。<ol>
<li>用两个平镜在分色镜后, 堵住泵梁并沿直线方向引导探头束。</li>
		<li>从靠近腔室的位置移除聚焦透镜, 将其置于探头光束路径中, 以确保探头光束穿过其中心。</li>
		<li>使用可变钕滤波器将探头光束能量最小化, 并添加额外的 nd 滤波器以衰减100新泽西州以下的脉冲能量。</li>
		<li>将紧凑型 CMOS 相机放在手动的线性平移阶段, 并将其连接到具有适当数据采集软件的计算机上。在探头光束路径上装入平移阶段, 以靠近光束焦距的摄像机为中心。使用软件程序定位光束点。添加 ND 滤波器并调整相机采集设置, 以防止 CMOS 探测器的饱和。</li>
		<li>调整平移阶段的位置以获得最小、最强的激光光斑。这个位置对应于光束的焦点。</li>
		<li>在聚焦处获取相机图像, 并利用适当的数据分析软件确定光束直径, 使光斑适合于二维高斯函数。</li>
		<li>卸下将探头光束定向到照相机的镜像, 并将聚焦透镜返回到其在飞行前的位置。</li>
	</ol></li>
	<li>水泵探头空间和时间重叠的测定 注意: 假定在步骤3.1 中完成协议。虽然氙气体可以作为样本来确定空间和时间重叠, 建议使用目标分子进行研究, 因为质量频谱的变化可以观察到一系列的正时滞, 而不是只有在零时滞, 和氙气一样。<ol>
<li>将所需的样品连接到飞行室, 并将压力调整到 1-5 x 10-7乇的范围内。</li>
		<li>解除对泵和探头光束的解锁, 并确保它们与飞行时-MS 室对齐。</li>
		<li>通过调整 ND 滤波器, 使探头功率最大化。将泵浦功率与 waveplate 设置为足够高的电平以获得满意的离子信号。 注: 探头功率应足够高, 以诱导破碎, 但不太高, 以创造离子在没有泵浦脉冲。</li>
		<li>调整探头光束的空间位置, 在分色镜架上的旋钮 (DC,图 1), 直到所有离子强度的峰值被观察到 (如果舞台位置恰好是在零延迟) 或显著耗尽母体分子离子和/或增加片段离子产量被观察 (如果阶段位置对应于一个正时滞)。</li>
		<li>如果没有观察到离子信号的变化, 则阶段位置可能在负时滞, i., 探头在泵之前。将机动延迟阶段调整为探头光束的较长路径, 并重复步骤3.3.4 直到观察到质量谱的变化。</li>
		<li>调整机动延迟阶段位置, 产生总离子信号的峰值。此位置对应于零时间延迟。如图 3所示, 在零时滞时, 具有良好和较差的空间重叠的分子 DMMP 的代表性质谱, 以及仅采用泵束的质谱。</li>
	</ol></li>
	<li>交叉相关6,34 注: 交叉相关测量必须在惰性气体 (如氙32) 上进行。验证了用青蛙测量的脉冲持续时间和零时滞对应的延迟阶段位置。<ol>
<li>与氙气体在房间 (步骤 3.1) 和光束重叠优化 (步骤 3.3), 移动机动化的阶段位置定位零时滞 (i., 当氙+信号最大化)。</li>
		<li>将机动化的翻译阶段扫描-200 fs 至 +200 fs 的延迟范围, 步骤为 5 fs。此扫描对应于在零时间延迟位置以120µm 为中心的1.5 µm 的步骤。记录质量谱在每个扫描位置和集成氙+收益率获得时间依赖的离子信号34。</li>
	</ol></li>
</ol>4. 水泵探头测量
<ol><li>采取测量前的初步检查<ol>
<li>检查实验设置以确认两个光束通过腔室的窗口传播 collinearly (图 1)。</li>
		<li>将所需样品连接到飞行室, 并逐步将样品放入腔内, 使用可变的检漏阀, 以达到 1-5 x 10-7乇的靶压力。在调整采样压力时, 确保在时间上关闭 MS 电源电压, 以避免由于压力峰值而对 MCP 探测器造成损坏。</li>
		<li>如果分子的蒸气压过低, 无法产生所需的压力, 请轻轻加热试样保持器, 直到达到所需的压力。</li>
		<li>打开并检查 MS 电压 (步骤 3.1.5)。验证数据采集软件在与机动延时阶段和示波器的通信方面的可操作性。</li>
		<li>调整腔体前面的透镜 (步进 3.1.7) 和泵浦探头的空间对准 (步骤 3.3.4), 优化离子信号和空间重叠。</li>
	</ol>
</li>
	<li>数据采集<ol>
<li>调整泵和探头脉冲能量以获得所需的离子信号。</li>
		<li>在数据采集软件中, 指定扫描长度和步骤大小。 注: 我们实验的典型扫描长度范围从 1000-5000 fs 和步骤大小不等, 从 5-20 fs19,20。</li>
		<li>运行数据采集软件, 在每次泵探头延迟时获取质量频谱。 注: 通常情况下, 每次扫描时延迟记录的质量频谱平均为1000激光射击。为了获得足够高的信噪比, 10-20 扫描在所需的设置(i., 扫描长度, 步长, 泵和探头功率) 和平均值。为了尽量减少激光功率漂移的影响, 可以在延迟阶段旅行的交替方向进行扫描。所有数据都保存为制表符分隔的文本文件。如图 4所示, 以 5 fs 的步长为 1250年 fs 的扫描长度的单扫描 DMMP 中的代表性原始质量光谱数据。</li>
	</ol>
</li>
	<li>数据处理<ol>
<li>确定每个质量峰值的飞行时间范围 (图 4中括号内的区域所示), 并在每个质量谱中集成这些范围。输出表示每个感兴趣的时间分辨信号。例如, DMMP 母体分子离子的时间分辨离子信号具有良好的和较差的泵探针空间重叠, 从一个泵浦探针扫描, 如图 5所示。</li>
		<li>重复步骤4.3.1 以获得所需的扫描数量 (e., 10-20)19,20在相同的扫描设置。平均每个时间分辨离子信号在所有扫描采取。典型的平均离子信号如图 6所示。</li>
	</ol>
</li>
</ol>

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作者没有什么可透露的。

该协议使我们能够通过选择性地在基态电子态中制备离子来解决原子基阳离子中的超快振动动力学问题。当标准强场电离过程使用800毫微米能准备振动相干在地线电子状态根本阳离子第一列 diatomics10,11,12,13并且 CO214,15, 多原子离子中多个离子激发态?...

自1960年激光发明以来, 有选择地打破分子中化学键的目标一直是化学家和物理学家的长期梦想。据信, 调整激光频率和强度的能力, 使目标键通过选择性能吸收在相关的振动频率1,2,3,4 的直接劈裂..然而, 早期的实验发现, 分子内的吸收能量的分子内振动再分配往往导致最弱键4,5的非选择性解切。直到飞秒脉冲激光器的发展和泵探针技术6在1980后期, 直接操纵相干振动状态, 或 "波包", 成功地控制了键分裂和其他目标6、7、8。泵探头测量, 其中 "泵" 脉冲准备一个兴奋的状态或离子, 随后被延迟的 "探针" 脉冲激发, 仍然是最广泛使用的技术研究分子9的超快过程, 10,11,12,13,14,15,16,17,18, 19,20。
用泵-探针激发耦合质谱检测法研究多原子自由基阳离子超快离解动力学的一个重要局限性是由电离泵非选择性靶分子的碎片化产生的。脉冲在 Ti: 蓝宝石波长800毫微米21,22,23。这种过剩的碎片起因于非绝热多光子电离, 可以通过将激发波长转换为近红外线 (e., 1200-1500 nm)22,23,24, 来减轻 25。在这些较长的波长, 绝热电子隧穿的贡献相对于多光子激发在电离过程22,23。绝热隧道给分子和形成主要地 "冷的地面状态分子离子19,22,23给少量多余的能量。我们以前的研究表明, 近红外激发的使用大大改善了相干振动激发的制备, 或 "波包", 在多原子自由基阳离子中, 与 800 nm 激发19相比, 20。这项工作将说明用 1500 nm 和 800 nm 在化学战剂模拟二甲磷酸 (DMMP) 上进行的泵探针测量, 以多光子为主的强场电离与隧道贡献的区别。泵波长。
在我们的泵探针实验中, 一对超短激光脉冲是时间延迟, 重组, 并聚焦到飞行时间的质谱仪, 如图 1中的设置所示。这些实验需要钛: 蓝宝石再生放大器生产 > 2 兆焦耳, 800 毫微米, 30 fs 脉冲。放大器输出在 90:10 (%R:%T) 光束分配器上拆分, 其中大部分能量用于为 1200年-1600 nm、100-300 µJ、20-30 fs 脉冲的生成提供一个光学参量放大器。红外泵束的直径扩展到22毫米, 800 nm 探针光束的直径向下-准直至5.5 毫米, 并使用虹膜进行芯核。这些 collimations 导致泵束聚焦于明显较小的束腰 (9 µm) 比探头束 (30 µm), 从而确保在电离泵脉冲形成的所有离子被延时探针脉冲激发。使用这种配置是因为我们的实验目的是探索母体分子离子的动力学, 即使是在聚焦光束边缘附近的较低强度下也可以形成。我们注意到, 如果更多的高激发离子物种的动力学是感兴趣的, 那么探头的光束直径应该比泵更小。
泵和探针脉冲传播 collinearly, 并集中在提取区域的威利-迈凯轮飞行时间质谱仪 (26 ) (图 2)。分子样品放置在一个小瓶连接到入口, 并打开到真空。此设置要求正在调查的分子具有非零的蒸气压;对于低蒸气压的分子, 瓶子可能会加热。气体样品流入燃烧室的流量由两个可变泄漏阀控制。样品进入房间通过一个 1/16 "不锈钢管大约 1 cm 离激光焦点 (图 2) 为了交付一个地方高集中目标分子在提取区域27。该萃取板有一个0.5 毫米狭缝定向正交到激光传播和离子路径。由于泵浦光束的瑞利范围约为2毫米, 这一狭缝用作过滤器, 只允许从中心焦量产生的离子, 在强度最高的情况下通过萃取板28。离子进入1米无场漂移管, 以达到 Z 隙微通道板 (MCP) 探测器29, 在那里他们被发现, 并记录与 1 GHz 数字示波器在1赫重复率的典型商业 Ti: 蓝宝石激光器。

<table>
	<tbody>
		<tr>
			<td>Mass spectrometer components</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TOF lens stack and flight tube assembly</td>
			<td>Jordan TOF Products, Inc.</td>
			<td>C-677</td>
			<td></td>
		</tr>
		<tr>
			<td>18 mm Z-gap detector assembly</td>
			<td>Jordan TOF Products, Inc.</td>
			<td>C-701Z</td>
			<td></td>
		</tr>
		<tr>
			<td>TOF high voltage power supply</td>
			<td>Jordan TOF Products, Inc.</td>
			<td>D-603</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum system components</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rotary vane backing pump</td>
			<td>Edwards Vacuum LLC</td>
			<td>RV12</td>
			<td></td>
		</tr>
		<tr>
			<td>Turbomolecular pumps (2)</td>
			<td>Edwards Vacuum LLC</td>
			<td>EXT255H</td>
			<td></td>
		</tr>
		<tr>
			<td>Turbomolecular pump controllers (2)</td>
			<td>Edwards Vacuum LLC</td>
			<td>EXC300</td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure gauge</td>
			<td>Edwards Vacuum LLC</td>
			<td>AIGX-S-DN40CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Chiller for water cooling</td>
			<td>Neslab</td>
			<td>CFT-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Femtosecond laser system</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ti:Sapphire regenerative amplifier</td>
			<td>Coherent, Inc.</td>
			<td>Astrella</td>
			<td>oscillator and amplifier in a single integrated system</td>
		</tr>
		<tr>
			<td>Optical Parametric Amplifer (OPA)</td>
			<td>Light Conversion</td>
			<td>TOPAS Prime</td>
			<td></td>
		</tr>
		<tr>
			<td>Motion control</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Motorized linear translation stage 1&#34; travel</td>
			<td>Thorlabs</td>
			<td>Z825B</td>
			<td></td>
		</tr>
		<tr>
			<td>controller for linear translation stage</td>
			<td>Thorlabs</td>
			<td>KDC 101</td>
			<td></td>
		</tr>
		<tr>
			<td>USB controller hub and power supply</td>
			<td>Thorlabs</td>
			<td>KCH 601</td>
			<td></td>
		</tr>
		<tr>
			<td>Manual linear translation stage 1&#34; travel</td>
			<td>Thorlabs</td>
			<td>PT1</td>
			<td></td>
		</tr>
		<tr>
			<td>Detectors</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pyroelectric laser energy meter</td>
			<td>Coherent, Inc.</td>
			<td>1168337</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermal laser power meter</td>
			<td>Coherent, Inc.</td>
			<td>5356E16R</td>
			<td></td>
		</tr>
		<tr>
			<td>Si-biased detector 200-1100 nm</td>
			<td>Thorlabs</td>
			<td>DET10A</td>
			<td></td>
		</tr>
		<tr>
			<td>Compact USB CMOS Camera</td>
			<td>Thorlabs</td>
			<td>DCC1545M</td>
			<td></td>
		</tr>
		<tr>
			<td>USB spectrometer</td>
			<td>Ocean Optics</td>
			<td>HR4000</td>
			<td></td>
		</tr>
		<tr>
			<td>1 GHz digital oscilloscope&#160;</td>
			<td>LeCroy</td>
			<td>WaveRunner 610Zi</td>
			<td></td>
		</tr>
		<tr>
			<td>Optics</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Type 1 BBO crystal</td>
			<td>Crylight Photonics</td>
			<td>BBO007</td>
			<td>aperture and thickness may be customized</td>
		</tr>
		<tr>
			<td>Achromatic half wave plate, 1100-2000 nm</td>
			<td>Thorlabs</td>
			<td>AHWP05M-1600</td>
			<td></td>
		</tr>
		<tr>
			<td>Wollaston prism polarizer</td>
			<td>Thorlabs</td>
			<td>WPM10</td>
			<td></td>
		</tr>
		<tr>
			<td>Hollow retro-reflector</td>
			<td>PLX, Inc.</td>
			<td>OW-20-1C</td>
			<td></td>
		</tr>
		<tr>
			<td>Variable neutral density filter</td>
			<td>Thorlabs</td>
			<td>NDC-100C-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Longpass dichroic mirror 2&#34; diameter</td>
			<td>Thorlabs</td>
			<td>DMLP950L</td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Digital Camera image software</td>
			<td>Thorlabs</td>
			<td>ThorCam</td>
			<td></td>
		</tr>
		<tr>
			<td>Instrument communication interface</td>
			<td>National Instruments</td>
			<td>NI-MAX</td>
			<td></td>
		</tr>
		<tr>
			<td>Graphical development environment for measurement programs</td>
			<td>National Instruments</td>
			<td>LabVIEW</td>
			<td></td>
		</tr>
		<tr>
			<td>Data processing software</td>
			<td>Mathworks</td>
			<td>MATLAB</td>
			<td></td>
		</tr>
	</tbody>
</table>

measurement of ultrafast vibrational coherences in polyatomic radical cations with strong-field adiabatic ionization

提出了一种在多原子自由基阳离子中制备振动相干的泵探针法, 并对其超快动力学进行了探讨。通过将强场电离泵脉冲的波长从常用的 800 nm 转换为近红外 (1200-1600 nm), 绝热电子隧穿对电离过程的贡献相对于多光子吸收增加。绝热电离结果在电子去除时, 离子的地面电子状态的主要人口, 有效地准备一个连贯的振动状态 ("波浪分组") 服从随后励磁。在实验中, 用弱场 800 nm 脉冲和在飞行时间质谱仪中测量的离解产物的时间依赖率来探测相干振动动力学。我们提出了分子二甲基磷酸 (DMMP) 的测量, 以说明如何使用 1500 nm 脉冲来提高离子产生相干振荡的振幅, 其系数为 10, 与 800 nm 脉冲相比。本协议可在现有的水泵探头设置中实现, 方法是将光学参量放大器 (.) 引入波长转换。

给出了21分子 DMMP 的结果。图 3显示了在零时间延迟时以 1500 nm 泵的峰值强度和 800 nm 探针脉冲分别为 8 x 1013和 8 x 1012 W 厘米-2的 DMMP 质谱。为参考, 还显示了仅用泵浦脉冲的质量谱。光谱是平均1万激光射击 (总承购时间十二年代)。当泵与探头梁之间的空间重叠优化 (绿色光谱) 时, 标记为 * 的离子信号的增加?...

Watch this Scientific Journal Video about Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization at JoVE.com

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization

我们提出了一个方法来探测超快振动相干的原子基阳离子, 导致分子离解。

强场绝热电离多原子自由基阳离子超快振动相干的测量

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the ...

measurement-ultrafast-vibrational-coherences-polyatomic-radical

Universidad San Sebastian

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Chemistry

Chemical Bonding: Basic Concepts

SCIENTISTS IN ACTION

6.8K 次观看.  Virginia Commonwealth University. 我们提出了一个方法来探测超快振动相干的原子基阳离子, 导致分子离解。

视频: Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization

A Study of the Complexation of Mercury(II) with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry

In this study we evaluated a method for the characterization of complexes, formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptide, by electrospray ionization orbitrap mass spectrometry. This strategy is based on previous successful characterization of mercury-dicysteinyl complexes involving tripeptides by utilizing mass spectrometry among other techniques. Mercury(II) chloride and a dicysteinyl tetrapeptide were incubated in a degassed buffered medium at varying stoichiometric ratios. The complexes formed were subsequently analyzed on an electrospray mass spectrometer consisting of a hybrid linear ion- and orbi- trap mass analyzer. The electrospray ionization mass spectrometry (ESI-MS) spectra were acquired in the positive mode and the observed peaks were then analyzed for distinct mercury isotopic distribution patterns and associated monoisotopic peak. This work demonstrates that an accurate stoichiometry of mercury and peptide in the complexes formed under specified electrospray ionization conditions can be determined by using high resolution ESI MS based on distinct mercury isotopic distribution patterns.

A Study of the Complexation of MercuryII with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry

The characterization of complexes formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptides by electrospray ionization orbitrap mass spectrometry is presented.

汞（II）与Dicysteinyl四肽的络合的电喷雾质​​谱研究

In this study we evaluated a method for the characterization of complexes, formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptide, ...

科研

化学

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

使用苝作为可见光光催化功能化的乙烯基单体原子转移自由基聚合

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

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 ...

Fabrication and Testing of Photonic Thermometers

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being leveraged for developing sophisticated photonic sensors. Silicon photonic sensors seek to exploit the strong confinement of light in nano-waveguides to transduce changes in physical state to changes in resonance frequency. In the case of thermometry, the thermo-optic coefficient, i.e., changes in refractive index due to temperature, causes the resonant frequency of the photonic device such as a Bragg grating to drift with temperature. We are developing a suite of photonic devices that leverage recent advances in telecom compatible light sources to fabricate cost-effective photonic temperature sensors, which can be deployed in a wide variety of settings ranging from controlled laboratory conditions, to the noisy environment of a factory floor or a residence. In this manuscript, we detail our protocol for the fabrication and testing of photonic thermometers.

We describe the process of fabrication and testing of photonic thermometers.

光子温度计的制作与测试

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being ...

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to the gas phase, and efficiently transferred to a detection system. Fizzy extraction takes advantage of the effervescence phenomenon. First, a carrier gas (here, carbon dioxide) is dissolved in the sample by applying overpressure and stirring the sample. Second, the sample chamber is decompressed abruptly. Decompression leads to the formation of numerous carrier gas bubbles in the sample liquid. These bubbles assist the release of the dissolved analyte species from the liquid to the gas phase. The released analytes are immediately transferred to the atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The ionizable analyte species give rise to mass spectrometric signals in the time domain. Because the release of the analyte species occurs over short periods of time (a few seconds), the temporal signals have high amplitudes and high signal-to-noise ratios. The amplitudes and areas of the temporal peaks can then be correlated with concentrations of the analytes in the liquid samples subjected to fizzy extraction, which enables quantitative analysis. The advantages of fizzy extraction include: simplicity, speed, and limited use of chemicals (solvents).

Fizzy extraction is a new laboratory technique for analysis of volatile and semivolatile compounds. A carrier gas is dissolved in the liquid sample by applying overpressure and stirring the sample. The sample chamber is then decompressed. The analyte species are liberated to the gas phase due to effervescence.

挥发性有机化合物与大气压化学电离四极杆质谱联用

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to ...

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) Mass Spectrometry

There are many techniques that can be employed in the characterization of synthetic homopolymers, but few provide as useful of information for end group analysis as matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). This tutorial demonstrates methods for optimization of the sample preparation, spectral acquisition, and data analysis of synthetic polymers using MALDI-TOF MS. Critical parameters during sample preparation include the selection of the matrix, identification of an appropriate cationization salt, and tuning the relative proportions of the matrix, cation, and analyte. The acquisition parameters, such as mode (linear or reflector), polarization (positive or negative), acceleration voltage, and delay time, are also important. Given some knowledge of the chemistry involved to synthesize the polymer and optimizing both the data acquisition parameters and the sample preparation conditions, spectra should be obtained with sufficient resolution and mass accuracy to enable the unambiguous determination of the end groups of most homopolymers (masses below 10,000) in addition to the repeat unit mass and the overall molecular weight distribution. Though demonstrated on a limited set of polymers, these general techniques are applicable to a much wider range of synthetic polymers for determining mass distributions, though end group determination is only possible for homopolymers with narrow dispersity.

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight MALDI-TOF Mass Spectrometry

A protocol for the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) characterization of synthetic polymers is described including the optimization of sample preparation, spectral acquisition, and data analysis.

基质辅助激光解吸电离飞行时间 (MALDI) 质谱法表征合成聚合物

There are many techniques that can be employed in the characterization of synthetic homopolymers, but few provide as useful of information for end group ...

An Efficient Sample Preparation Method to Enhance Carbohydrate Ion Signals in Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Sample preparation is a critical process in mass spectrometry (MS) analysis of carbohydrates. Although matrix-assisted laser desorption/ionization (MALDI) MS is the method of choice in carbohydrate analysis, poor ion signal and data reproducibility of carbohydrate samples continue to be severe problems. For quantitative analysis of carbohydrates, an effective analytical protocol providing superior data quality is necessary. This video demonstrates sample preparation protocols to improve signal intensity and minimize data variation of carbohydrates in MALDI-MS. After drying and crystallization of sample droplets, the crystal morphology is reformed by methanol before mass spectrometric analysis. The enhancement in carbohydrate signal is examined with MALDI imaging mass spectrometry (IMS). Experimental results show that crystal reformation adjusts crystalline structures and redistributes carbohydrate analytes. In comparison with the dried droplet preparation method in conventional MALDI-MS, reforming carbohydrate crystal morphologies with methanol shows significantly better signal intensity, ion image distribution, and data stability. Since the protocols demonstrated herein do not involve changes in sample composition, they are generally applicable to various carbohydrates and matrixes.

A protocol for enhancing carbohydrate ion signals in MALDI mass spectrometry by reforming crystalline structures during sample preparation processes is demonstrated.

基质辅助激光解吸/电离质谱中增强碳水化合物离子信号的高效样品制备方法

Sample preparation is a critical process in mass spectrometry (MS) analysis of carbohydrates. Although matrix-assisted laser desorption/ionization (MALDI) ...

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

解析高强共聚物芳纶纤维使其力学性能的测定

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

High Resolution Physical Characterization of Single Metallic Nanoparticles

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single nanometer-scale pore. The signal is characteristic of the molecule&#39;s physicochemical properties and its interactions with the pore. We demonstrate that the nanopore formed by the bacterial protein exotoxin Staphylococcus aureus alpha hemolysin (&#945;HL) can detect polyoxometalates (POMs, anionic metal oxygen clusters), at the single molecule limit. Moreover, multiple degradation products of 12-phosphotungstic acid POM (PTA, H3PW12O40) in solution are simultaneously measured. The single molecule sensitivity of the nanopore method allows for POMs to be characterized at significantly lower concentrations than required for nuclear magnetic resonance (NMR) spectroscopy. This technique could serve as a new tool for chemists to study the molecular properties of polyoxometalates or other metallic clusters, to better understand POM synthetic processes, and possibly improve their yield. Hypothetically, the location of a given atom, or the rotation of a fragment in the molecule, and the metal oxidation state could be investigated with this method. In addition, this new technique has the advantage of allowing the real-time monitoring of molecules in solution.&#160;

Here, we present a protocol to detect discrete metal oxygen clusters, polyoxometalates (POMs), at the single molecule limit using a biological nanopore-based electronic platform. The method provides a complementary approach to traditional analytical chemistry tools used in the study of these molecules.

单金属纳米粒子的高分辨率物理特性

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single ...

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional &#960;-conjugate Systems

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near infrared (near-IR) transitions, because it can overcome the low sensitivity of spontaneous Raman spectrometers in the near-IR region. Here, we describe technical details of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer that we have recently developed. A description of signal generation and optimization, measurement, data acquisition, and calibration and correction of recorded data is provided as well. We present an application of our spectrometer to analyze the excited-state dynamics of &#946;-carotene in toluene solution. A C=C stretch band of &#946;-carotene in the second lowest excited singlet (S2) state and the lowest excited singlet (S1) state is clearly observed in the recorded time-resolved stimulated Raman spectra. The femtosecond time-resolved near-IR stimulated Raman spectrometer is applicable to the structural dynamics of &#960;-conjugate systems from simple molecules to complex materials.

Details of signal generation and optimization, measurement, data acquisition, and data handling for a femtosecond time-resolved near-IR stimulated Raman spectrometer are described. A near infrared stimulated Raman study on the excited-state dynamics of &#946;-carotene in toluene is shown as a representative application.

超快时间解析近红外刺激拉曼测量功能 +偶联系统

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near ...