Chemical Morphology of Carbonaceous Particulates and Their Precursors in Diffusion Flames

明亮的黄色辉光是大多数火灾和火焰的普遍特征，任何见过壁炉或壁炉外的蜡烛或火焰的人都会将其与燃烧联系起来。这种排放来自非常热的纳米级颗粒，主要是碳，沿着还有少量的其他元素，特别是氢。考虑到这些粒子在人类火灾和燃烧体验中的核心作用，值得注意的是，它们是如何形成的细节并不完全清楚。 怎么会这样？ 一个原因是，发生的过程发生得非常快。这些粒子可能含有一百万个碳原子，它们是在不到一秒钟的时间内从只含有几个碳原子的分子中组装起来的。 因此，这种化学反应涉及数千（也许数百万）个连续的步骤和同样多的中间体。 更糟糕的是，用于研究“煤烟”形成的一套实验室诊断方法通常会给我们提供关于非常小或非常大的中间体的信息，而这两者之间发生的事情却存在很大的不确定性。在这项资助中，乔治华盛顿大学的一组研究人员正在将一套基于激光的诊断方法应用于简单且特征明确的实验室火焰中烟尘形成的研究。 除了本实验室提供的“传统”诊断外，还将引入一套基于一类新兴的“超连续谱”光源的新测量方法。从本质上讲，这些光源是“白光激光器”，其中产生的光束覆盖了广泛的颜色。 其中一个光源产生可见光（以及刚好超出人类感知范围的光），将用于研究最小煤烟颗粒中电子的行为。 第二个产生红外光，提供有关颗粒结构的额外信息;特别是单个碳原子如何相互结合。这两种类型的诊断都旨在提供对在分子生长的最早阶段形成的“新生”烟灰颗粒的结构的洞察。除了这项实验工作外，计算工具将用于预测粒子结构，目的是验证实验室结果。地球上的烟尘形成在能源生产中起着关键作用（来自商用锅炉中炉壁的烟灰涂层，烟灰颗粒撞击在商用飞机发动机的涡轮机叶片上）和环境中（从城市地区死亡率上升到加剧气候变化）。 值得注意的是，在整个宇宙中发现了相同类型的物种（可能是通过类似的过程形成的），并被认为是一些最有趣（和难以捉摸）的天文观测的原因。这一点和米勒实验室的整个先前NSF支持的工作的主要重点是博士生的教育。 实验室校友的成功记录已经得到证实。四的最后五个博士学位授予从这个研究小组申请并获得了著名的政府博士后奖学金。至少有三名校友已经成长为国防部，商务部和NASA实验室的高级管理职位。 其中一位现在在白宫的科技政策办公室工作。 此外，该实验室在STEM领域传统上代表性不足的性别和种族的教育方面有着良好的记录。 在这个补助金，传统将继续提供研究经验的博士生，本科生和高中生从哥伦比亚特区高中画。

A bright yellow glow is a ubiquitous feature of most fires and flames and is associated with combustion by anyone who has ever seen a candle or a fire in a fireplace or outside. This emission is from very hot, nanometer-sized particles of mostly carbon, along with smaller quantities of some other elements, especially hydrogen. Given the central role that these particles hold in the human experience with fires and combustion, it is remarkable that the details of how they are formed are not fully known. How can this be? One reason is that the processes that occur happen very quickly. These particles, that contain perhaps a million carbon atoms, are assembled in times of less than a second from molecules that contain only a few carbon atoms. Thus, this chemistry involves thousands (perhaps millions) of successive steps and just as many intermediates. To compound the problem, the suite of laboratory diagnostics that have been applied to the study of "soot" formation typically gives us information about very small or very large intermediates, leaving a great deal of uncertainty about what happens in between. In this grant, a team of researchers at George Washington University is applying a suite of laser-based diagnostics to a study of soot formation in simple and well-characterized, laboratory flames. In addition to "traditional" diagnostics available in this laboratory, a new suite of measurements will be introduced based on a class of emerging "super continuum" light sources. In essence, these sources are "white-light lasers" where a beam of light is created covering a wide range of colors. One of these sources produces visible light (and light just beyond the range of human perception) and will be used to study the behavior of electrons in the smallest soot particles. The second produces infrared light that provides additional information on particle structure; specifically how individual carbon atoms are bound to one another. Both types of diagnostics are intended to provide insight to the structure of "nascent" soot particles formed at the earliest stages of molecular growth. In addition to this experiment work, computational tools will be used to predict particle structures, with a goal of validation of the laboratory results.Soot formation on earth plays a critical role in energy generation (from the soot coating of furnace walls in a commercial boiler, to soot particle impingement on the turbine blades of a commercial aircraft engine) and in the environment (from increasing mortality in urban areas to contributing to climate change). Remarkably, the same types of species (perhaps formed through similar processes) are found throughout the universe and are thought to be responsible for some of the most intriguing (and elusive) astronomical observations. A primary focus of this and the Miller Lab's entire prior NSF supported work has been the education of doctoral students. There has been a proven record of success by laboratory alumni. Four of the last five Ph.D.s to be awarded from this research group applied for and were awarded prestigious government postdoctoral fellowships. At least three of the alumni have grown into senior management positions at laboratories of the Department of Defense, Commerce, and NASA. One now serves in the Office of Science and Technology Policy at the White House. Further, the laboratory has a proven record of education of traditionally underrepresented genders and races in STEM fields. In this grant, the tradition will be continued by providing research experience for doctoral students, undergraduates, and high school students drawn from District of Columbia high schools.