Infrared emission from the quenching of electronically excited states

电子激发态淬灭产生的红外发射

• 批准号: EP/L025833/1
• 负责人: Grant Ritchie
• 金额: $ 43.1万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FL025833%2F1
• 关键词: Infrared; emission; quenching; electronically; excited

When a molecule absorbs light to form an excited state, its total energy increases, it is no longer in equilibrium with its surroundings, and processes will naturally occur to counteract this and thereby restore equilibrium. For an electronically excited bound state (where the absorption is in the visible or ultraviolet region of the spectrum), the process of energy loss can take place through emission of light (fluorescence) or by collisional processes (quenching). Fluorescence is well understood, as are the rates of quenching, but what is far less understood are the specific fates of the quenched species - where does the (considerable) energy contained in the excited state go - does it appear in kinetic or internal energy of the ground state product and if chemical reaction is possible, what are the products and are they formed with internal energy? The purpose of this study is to investigate the products of the quenching of two important gas phase free radical species, OH and NO. They will be formed in their electronically excited states by absorption of ultraviolet photons (at 308 nm and 226 nm respectively), and the products observed by the technique of Time Resolved Fourier Transform InfraRed Emission (TRFTIRE) using an apparatus unique to the UK. The first system to be studied will be the quenching of the OH(A) state in collisions with molecular hydrogen. Here the main result of quenching is the formation of water, and preliminary results have shown that the water is hot, with a great deal of the available energy appearing as vibration, and resulting in emission in the mid-infrared region of the spectrum. The emission spectrum of H2O will be compared with the complementary results already obtained for this reaction by Lester's group on the H atom cofragment kinetic energy distribution, and the internal energy distribution in the OH ground state product of inelastic quenching. State of the art calculations of the quenching processes will be carried out by our theoretical partners. Other systems to be studied include the quenching of OH(A) by O2, CO and CO2, where atomic reaction products have been observed - our studies will complete the picture by looking for the first time at the molecular reaction products. Similar studies on the NO(A) state will also be carried out. The results are of importance in interpreting the laser induced fluorescence measurements in combustion systems, where quenching processes can result in a serious overestimation of the radical concentrations.

当分子吸收光以形成激发态时，其总能量会增加，它不再与周围环境保持平衡，并且自然会发生过程来抵消这一问题并恢复平衡。对于电子激发的结合态（在光谱的可见或紫外线中的吸收），可以通过发射光（荧光）或碰撞过程（淬灭）进行能量损失过程。荧光和淬火速率都广为人知，但是，猝灭物种的特定命运要少得多 - 激发态在何处所包含的（相当多的）能量在何处，它是否在基础态产物的动力学或内部能量中出现，如果化学反应是可能的，它们是什么，它们是什么产品，它们是内部能量的吗？这项研究的目的是研究两个重要的气相自由基物种淬灭的产物，哦，没有。它们将通过吸收紫外光子（分别在308 nm和226 nm）以及使用英国特有的设备来解决的傅立叶变换红外发射（TRFTIRE），在电子激发态中形成。第一个要研究的系统将是与分子氢碰撞中OH（a）状态的淬灭。这里的主要结果是水的形成，初步结果表明水很热，可用的能量出现为振动，并在光谱的中红外区域发射。 H2O的发射光谱将与Lester的组对H原子共块动能分布已经获得的互补结果进行比较，以及无弹性淬火基态的OH基态产物中的内部能量分布。淬灭过程的最新计算将由我们的理论伙伴进行。要研究的其他系统包括O2，CO和CO2的OH（A）淬灭，在该系统中观察到了原子反应产物 - 我们的研究将通过第一次寻找分子反应产物来完成图片。还将对NO（A）状态进行类似的研究。结果对于解释燃烧系统中激光诱导的荧光测量值至关重要，在这种燃烧系统中，淬火过程可能会导致对根部浓度的严重高估。