Competing Pathways in Reactions of Oxygen-Containing Free Radicals

含氧自由基反应中的竞争途径

• 批准号: 1301156
• 负责人: H. Floyd Davis
• 金额: $ 39.88万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-15 至 2016-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1301156&HistoricalAwards=false
• 关键词: Competing; Pathways; Reactions; Oxygen; Containing

Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms - A Program of the Division of Chemistry, Prof. H. Floyd Davis and students at Cornell University will study photoinduced and bimolecular reactions involving atmospherically important oxygen-containing free radicals. Using the crossed laser- molecular beam method, the branching ratios for competing bromine dioxide and iodine dioxide photodissociation pathways will be determined. Elementary radical-radical reactions involving diatomic halogen oxide free radicals (e.g., ClO + BrO) will be studied in crossed molecular beams. A method involving photodepletion of highly-reactive neutral halogen oxide molecules with near-threshold photoionization detection will be developed to determine wavelength-dependent absorption cross sections for species that cannot be prepared in pure form. The proposed studies will provide experimental benchmarks, including ionization energies, bond dissociation energies, and branching ratios for key atmospheric reactions induced by absorption of solar radiation or bimolecular collisions. These quantities should help facilitate direct tests of quantum theoretical models for reactions, and should be of use in atmospheric models for ozone-depleting processes. Halogen atoms (chlorine, bromine, and iodine) undergo reactions in the Earth's atmosphere that destroy ozone, an important molecule that provides protection from harmful ultraviolet solar radiation. The ozone-destroying reactions involve molecules with unpaired electrons known as free radicals. Because of their extremely reactive nature, most free radicals cannot be prepared in pure form, making their study difficult. In this research project, laboratory techniques involving laser beams (collimated beams of light) and molecular beams (collimated beams of molecules), are used to study chemical reactions involving atmospheric free radicals. In addition, the Davis group will establish a high-school lending program for newly-developed low-cost ($25) absorption spectrometers. This will help bring hands-on laboratory experiments, usually requiring high-cost equipment, to the high school classroom. Exposing high school students to the design, construction, and use of scientific instruments can be used to teach critical thinking skills and help students understand and appreciate science.

通过该奖项，由化学结构，动力学和机制资助 - 化学划分的计划，H。FloydDavis教授和康奈尔大学的学生将研究涉及大气中重要的含氧自由基的光诱导和双分子反应。 使用交叉的激光束法，将确定用于竞争的二氧化溴和二氧化二氧化碳光解离途径的分支比率。 将在交叉分子束中研究涉及双硅质氧化物自由基的基本自由基反应（例如CLO + BRO）。 将开发涉及高度反应性中性卤素氧化物分子具有接近阈值光电离检测的方法，以确定无法以纯形式制备的物种的波长依赖性吸收横截面。 拟议的研究将提供实验性基准，包括电离能，键解离能以及通过吸收太阳辐射或双分子碰撞引起的关键大气反应的分支比。 这些数量应有助于促进对反应的量子理论模型的直接测试，并应在大气模型中用于消耗臭氧的过程。卤素原子（氯，溴和碘）在地球大气中发生反应，破坏臭氧，这是一种重要的分子，可保护有害紫外线太阳辐射。 破坏臭氧的反应涉及分子，该反应被称为自由基的未配对电子。 由于其极其反应性的性质，大多数自由基不能以纯净的形式制备，从而使他们的学习变得困难。 在该研究项目中，涉及激光束（光束的光束）和分子束（分子的准束）的实验室技术用于研究涉及大气自由基的化学反应。 此外，戴维斯集团（Davis Group）将针对新发达的低成本（25美元）吸收光谱仪建立一项高中贷款计划。这将有助于将动手实验室实验（通常需要高成本设备）带到高中教室。可以将高中生的设计，建设和使用科学仪器用于教授批判性思维技能，并帮助学生理解和欣赏科学。