Laboratory Studies of O2 Excited States Relevant to the CO2 Planets

在金星、地球和火星的上层大气中，分子氧通过吸收太阳紫外线辐射而分解为原子氧。然后氧原子可以通过三体相互作用与另一个分子重组，形成处于激发态的分子氧。在金星和火星上，第三种分子是二氧化碳。光解、复合和扩散输运之间的竞争决定了中间层和低热层的原子和分子组成。准确的氧原子复合过程的知识是至关重要的建模的氧原子的高度分布的昼夜行为和解释从原子氧，分子氧，和羟基的夜光排放。在这个项目中，首席研究员和一名博士后研究员将进行实验室实验，研究在二氧化碳环境中O原子复合后产生的激发态分子氧的产率。来自受激准分子激光器的紫外光脉冲将在温度受控的气体流动池中维持的二氧化碳中光引发O原子复合。荧光和共振增强多光子电离（REMPI）技术将检测激发态氧分子，并确定激发态产生的氧原子重组和随后的二氧化碳弛豫的产量。这些测量需要量化金星和火星高层大气中的氧气气辉，并通过遥感探测其大气动力学。研究结果将有利于行星大气模型的建立，并将提高过去和未来金星和火星任务的科学回报。应用基础化学和物理学研究碰撞过程对于理解高功率化学激光器的运行也是至关重要的。最后，该项目将有助于博士后研究员和暑期本科生的培训和研究经验。

In the upper atmospheres of Venus, Earth, and Mars, molecular oxygen is dissociated into atomic oxygen by absorption of solar ultraviolet radiation. The oxygen atoms can then recombine through a 3-body interaction with another molecule to form molecular oxygen in an excited state. On Venus and Mars, the third molecule is carbon dioxide. The competition between photodissociation, recombination, and diffusive transport determines the atomic and molecular composition of the mesosphere and lower thermosphere. Accurate knowledge of the oxygen atom recombination processes is critical for modeling the diurnal behavior of the altitude profile of oxygen atoms and interpreting nightglow emissions from atomic oxygen, molecular oxygen, and hydroxyl. In this project, the Principal Investigator and a postdoctoral fellow will conduct laboratory experiments to study the yields of the excited molecular oxygen states generated following O-atom recombination in a carbon dioxide environment. An ultraviolet light pulse from an excimer laser will photoinitiate O-atom recombination in carbon dioxide, maintained in a temperature-controlled gas flow cell. Fluorescence and resonance enhanced multiphoton ionization (REMPI) techniques will detect excited oxygen molecules and determine the yields of the excited states produced following O-atom recombination and subsequent relaxation in carbon dioxide. These measurements are needed to quantify oxygen airglow in the upper atmospheres of Venus and Mars and to probe their atmospheric dynamics by remote sensing. The results will benefit modelers of planetary atmospheres and will enhance the scientific returns on past and future missions to Venus and Mars. Application of basic chemistry and physics to the study of collisional processes is also critical for understanding the operation of high-power chemical lasers. Finally, the project will contribute to the training and research experience of a postdoctoral fellow and summer undergraduate students.