State-resolved studies of the vibronic structure and reaction dynamics of molecular dications

分子双键的电子振动结构和反应动力学的状态分辨研究

• 批准号: EP/E038522/1
• 负责人: Stephen Price
• 金额: $ 49.72万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE038522%2F1
• 关键词: State; resolved; studies; vibronic; structure

Molecules which carry two positive charges, molecular dications, possess unusual properties. Firstly, due to the repulsion of the two like-charges the molecules are highly energetic. This high energy means that they react differently to singly-charged ions. Secondly, the repulsion between the two positive charges means than many of these doubly charged molecules are very short-lived and they fragment to form a pair of singly-charged ions. However, for most small molecules, certain arrangements of their electrons give strong enough chemical bonds to hold the molecule together despite the repulsion between the pair of positive charges. These arrangements of the electrons generate so-called long-lived ( metastable ) electronic states of molecular dications. In these metastable states many small molecular dications can live for long enough to collide with a neutral molecule and undergo chemical reactions. This application proposes an extensive upgrade to a piece of apparatus developed by the applicant to study the chemical reactions of molecular dications. The apparatus operates by identifying both of the charged products that usually are formed in a dication chemical reaction. The apparatus uses a specially designed mass spectrometer to detect and identify both of the charged products from reaction of an individual dication; a so-called coincidence experiment. Using a position-sensitive detector in the mass spectrometer allows the experiment to precisely determine how both of the product ions are moving following an individual reactive event. Such studies of the motion of the product ions, the so-called dynamics of a reactive process, provide a powerful probe of the mechanism of the chemical reaction. In it's current configuration the experiment has revealed the reactivity of a wide-range of dications and shown that dication reactions proceed by unusual pathways. However, the accuracy with which the experiment can probe the energies of the reaction products is currently limited and this application proposes significant developments to the spectrometer to dramatically improve this energy resolution. We propose to install a larger area detector and improved timing electronics, together the incorporation of a more controlled and constrained inlet (a molecular beam ) for the neutral molecules. These improvements, together with a new design of mass spectrometer which incorporates a velocity imaging methodology, will improve the energy resolution of the spectrometer so that the energies and reactivity of individual vibrational levels of diatomic dications can be determined. Velocity imaging is a technique developed for laser spectroscopy, involving a special arrangement of electric fields in the mass spectrometer, which allows the product ion velocities to be determined accurately. To implement velocity imaging in our experiment, which does not use a laser to ionize the products of the reaction, involves a new design of mass spectrometer, which we have developed, which still gives accurate product ion velocities but does not degrade the ability of the mass spectrometer to identify different species. We propose to use the upgraded apparatus to study the energy levels of diatomic dications which cannot be probed by existing techniques and also to study the reactivity and reaction mechanisms of the molecular dications which have recently been implicated as key species in the chemistry of planetary ionospheres.

带两个正电荷的分子，即分子指示，具有不寻常的性质。首先，由于两个类电荷的排斥，分子具有很高的能量。这种高能量意味着它们对单电荷离子的反应不同。其次，两个正电荷之间的斥力意味着这些双电荷分子的寿命非常短，它们会分裂成一对单电荷离子。然而，对于大多数小分子来说，它们的电子的某些排列方式产生了足够强的化学键，使分子结合在一起，尽管这对正电荷之间存在排斥。这些电子的排列产生所谓的分子指示的长寿命（亚稳态）电子状态。在这些亚稳态中，许多小分子能存活足够长的时间，与中性分子发生碰撞并发生化学反应。此申请建议对申请人开发的用于研究分子指示物的化学反应的仪器进行广泛升级。该装置通过识别通常在单一化学反应中形成的两种带电产物来工作。该仪器使用专门设计的质谱仪来检测和鉴定单个反应的带电产物；一个所谓的巧合实验。使用质谱仪中的位置敏感探测器，实验可以精确地确定两个产物离子在单个反应事件后是如何移动的。这种对产物离子运动的研究，即所谓的反应过程动力学，为化学反应的机理提供了强有力的探索。在它目前的结构中，实验揭示了大范围指示的反应性，并表明指示反应通过不寻常的途径进行。然而，实验可以探测反应产物能量的准确性目前是有限的，这一应用提出了对光谱仪的重大发展，以显着提高这种能量分辨率。我们建议安装一个更大的探测器和改进的定时电子设备，同时结合一个更受控制和约束的中性分子入口（分子束）。这些改进与采用速度成像方法的质谱仪的新设计一起，将提高光谱仪的能量分辨率，从而可以确定双原子指示物的单个振动能级的能量和反应性。速度成像是为激光光谱学开发的一种技术，它涉及到质谱仪中电场的特殊安排，从而可以准确地确定产物离子的速度。为了在我们的实验中实现速度成像，不使用激光电离反应产物，我们开发了一种新的质谱仪，它仍然可以给出准确的产物离子速度，但不会降低质谱仪识别不同物种的能力。我们建议使用升级后的仪器来研究现有技术无法探测的双原子指示物的能级，并研究最近被认为是行星电离层化学中的关键物种的分子指示物的反应性和反应机理。

项目成果

Electron ionization of CO2

CO2 的电子电离

• DOI: 10.1016/j.ijms.2008.02.008
• 发表时间: 2008
• 期刊: International Journal of Mass Spectrometry
• 影响因子: 1.8
• 作者: King S

Bond-forming reactions of small triply charged cations with neutral molecules.

小的三电荷阳离子与中性分子的成键反应。

• DOI: 10.1002/chem.201301861
• 发表时间: 2013
• 期刊: Chemistry (Weinheim an der Bergstrasse, Germany)
• 作者: Fletcher JD

Bond-forming reactions of N22+ with C2H4, C2H6, C3H4 and C3H6

N22 与 C2H4、C2H6、C3H4 和 C3H6 的成键反应

• DOI: 10.1016/j.ijms.2014.05.009
• 发表时间: 2015
• 期刊: International Journal of Mass Spectrometry
• 影响因子: 1.8
• 作者: Fletcher J

Electron transfer and bond-forming reactions following collisions of I 2+ with CO and CS 2

I 2 与 CO 和 CS 2 碰撞后的电子转移和成键反应

• DOI: 10.1080/00268976.2015.1007105
• 发表时间: 2015
• 期刊: Molecular Physics
• 影响因子: 1.7
• 作者: Fletcher J

Bond-forming and electron-transfer reactivity between Ar2+ and O2.

• DOI: 10.1039/d0cp01194k
• 发表时间: 2020-04
• 期刊: Physical chemistry chemical physics : PCCP
• 作者: Sam Armenta Butt;S. Price