Excitation and Emission Properties of Molecular Nitrogen for Earth's Thermosphere

地球热层氮分子的激发和发射特性

• 批准号: 0938223
• 负责人: Xianming Liu
• 金额: $ 29.01万
• 依托单位: Space Environment Technologies
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0938223&HistoricalAwards=false
• 关键词: Excitation; Emission; Properties; Molecular; Nitrogen

The investigators will combine experimental measurement and theoretical calculation to determine molecular nitrogen excitation and emission properties that are critical to the rate processes of nitrogen rich thermospheres. Molecular nitrogen is transparent to solar radiation from the infrared to the far ultraviolet where the forbidden Lyman-Birge-Hopfield and Vegard Kaplan band systems show weak, discrete absorption transitions. Strong absorption of solar radiation occurs in the extreme ultraviolet where the singlet ungerade electronic states show strong discrete blended structure. These states are closely spaced in energy and are strongly coupled. Many of them are strongly predissociative and a major source of chemical radicalization in the atmosphere. The strong coupling among the ungerade states results in very large rotational dependence of transition dipole matrix elements and predissociation yields. The strong rotational dependence in cross sections and predissociation yields requires that laboratory measurements must be translated to projected atmospheric temperature through modeling to avoid large errors. The impact of the strong rotational dependence has not been considered in many atmospheric models. Predissociation yields will be determined from a comparison of emission and excitation cross sections. The measured emission cross sections, together with the already measured, high resolution photoabsorption cross sections, will be utilized to determine the diabetic electronic transition moments. A coupled-channel model will be used to analyze the measurements and calculate spontaneous transition probabilities and predissociation yields. The research in this program connects the community concerned with the understanding of the thermosphere with researchers in laboratory geophysics and theoretical atomic and molecular physics. The program addresses fundamental physical properties of molecular nitrogen, which are critical to understanding the upper atmospheres of Earth, Titan and Triton. As such, the results of the work are applicable beyond the restricted targets identified here, and become a knowledge base for a broad range of disciplines. The program has extensive participation of undergraduate, graduate students and post-doctoral scholars.

研究人员将结合实验测量和理论计算，以确定对富含氮的热球速率过程至关重要的分子氮激发和发射特性。分子氮对从红外线到远紫外线的太阳辐射透明，而禁止的Lyman Birge-Hopfield和Vegard Kaplan带系统显示出弱，离散的吸收过渡。太阳辐射的强吸收发生在极端的紫外线中，在该紫外线中，单线出身电子状态显示出强烈的离散混合结构。这些状态在能量方面紧密距离，并密切相关。其中许多是强烈的预防性，并且是大气中化学激进化的主要来源。结合状态之间的强耦合导致过渡偶极基矩阵元件和预分离率的旋转依赖性非常大。横截面和预分离收益率的强旋转依赖性要求必须通过建模将实验室测量转换为预计的大气温度，以避免较大的误差。在许多大气模型中，尚未考虑强旋转依赖性的影响。预分离产率将从发射和激发横截面的比较来确定。测得的发射横截面以及已经测量的高分辨率光吸收横截面将用于确定糖尿病电子过渡矩。耦合通道模型将用于分析测量值并计算自发过渡概率和预分离收率。该计划中的研究将社区与对热圈的理解有关，研究人员与实验室地球物理学以及理论原子和分子物理学有关。该程序解决了分子氮的基本物理特性，这对于理解地球，泰坦和特里顿的上层大气至关重要。因此，工作结果适用于此处确定的限制目标，并成为广泛学科的知识库。该计划在本科生，研究生和博士后学者中广泛参与。