Collaborative Research: Laboratory Measurements of Oxygen (O) and Nitrogen (N2) Ultraviolet (UV) Cross Sections by Particle Impact for Remote Sensing of Thermosphere O/N2 Variation

合作研究：通过粒子撞击实验室测量氧气 (O) 和氮气 (N2) 紫外线 (UV) 截面，以遥感热层 O/N2 变化

• 批准号: 2031346
• 负责人: Joseph Evans
• 金额: $ 9.19万
• 依托单位: Computational Physics Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-15 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2031346&HistoricalAwards=false
• 关键词: Collaborative; Research; Laboratory; Measurements; Oxygen

Space-based remote sensing is widely used to measure the Earth’s atmosphere. Most of these measurements are based on detection of naturally occurring light emissions from the atmospheric molecules and atoms. To interpret these measurements correctly, understanding how the light emission occurs in these particles is of fundamental importance. A quantity called emission cross section is a key parameter that describes the emission process. While this parameter can sometimes be inferred from observation, laboratory measurement in a controlled environment is essential to provide a definitive estimate for such parameter. The goal of this project is to determine the UV emission cross sections needed for remote sensing observations of the Earth’s dayglow by NASA spacecraft. In the dayglow, a unique signature of the O/N2 column density ratio, derived from satellite-based UV observations, comes from the intensity ratio of the OI (135.6 nm) and N2 Lyman-Birge-Hopfield (LBH) band system (125-250 nm), both optically forbidden emissions. The O/N2 column density ratio is key to understanding ionosphere and thermosphere composition changes on a global scale under all geomagnetic conditions from Earth-orbiting satellites, e.g. GOLD (Global-scale Observation of the Limb and Disk). The team’s research in the last funding period shows laboratory spectroscopy for the past 50-years has failed to measure the cascade-induced UV spectrum and determine LBH vibrational intensities or cascade emission cross sections, which accounts for ~30% of the total emission cross section, of the Earth’s strongest FUV emission. This failure has precipitated a controversy in the literature that has persisted for over a decade due to the dichotomy between terrestrial airglow observations and forward model calculations. The project team have measured in the laboratory the FUV cascade-induced spectrum of the LBH band system of N2 excited by 30–200 eV electrons. The cascading transition begins with two processes: radiative and collision-induced electronic transitions (CIETs) involving two states (a and w), which are followed by a cascade induced transition a X. In this project, the team will investigate the threshold emission cross sections from 10-30 eV. The uniqueness of this project is the measurement of both the atomic O and molecular N2 absolute Qem (total emission cross section) and Qcasc (cascade-induced cross section) more accurately with a special apparatus designed with a ten times bigger collision chamber than previous laboratory measurements to properly account for the cascade contributions under the same experimental conditions.Laboratory spectroscopy at LASP has made a monumental step by measuring the optically-forbidden cascade-induced UV spectrum of N2 for the first time. However, much work needs to be done to complete the study of LBH and other important optically forbidden transitions that began in the first chamber (0.75 m radius). The second chamber with a radius of 2 m (more than double that of the first chamber) allows a whole new realm of atomic and molecular physics. The lifetime ranges available for laboratory studies of single scattering electron impact induced fluorescence spectra were 1-100ns (mainly allowed UV electronic transitions) for the past 50 years prior. With two large vacuum chambers at the University of Colorado even more highly forbidden transitions with lifetimes to 10ms can be studied to capture the full light emission and partial light emission to 100ms with an ability to model to 1000ms. This new field of physics involving optically forbidden transitions allows the study of spectra never before measured in single-scattering conditions such as that from LBH, the Cameron Bands of CO and Vegard-Kaplan band system of N2. The PIs of this proposal have an extensive 50 year track record of measuring the absolute Qem and Qcasc for atoms and molecules of interest to Earth and planetary atmospheres. The multi-facet approaches of both experiment and modeling promise a critical thermosphere parameter (O/N2) for an understanding of the Earth’s thermosphere and extending in scope to other planetary atmospheres. The project team’s data provides a bench-mark reference for high resolution studies by current and future satellite missions (e.g., Atmosphere-Space Interactions Monitor (ASIM) carrying a suite of instruments on the International Space Station).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

天基遥感被广泛用于测量地球大气层。 这些测量大多基于对大气分子和原子自然发生的光发射的检测。 为了正确解释这些测量结果，了解这些粒子中的光发射是如何发生的至关重要。 一个称为发射截面的量是描述发射过程的关键参数。 虽然这个参数有时可以从观察中推断出来，但在受控环境中进行的实验室测量对于提供这种参数的明确估计是必不可少的。 该项目的目标是确定美国航天局航天器对地球日光进行遥感观测所需的紫外线辐射截面。在日光中，来自卫星紫外观测的O/N2柱密度比的独特特征来自OI（135.6 nm）和N2 Lyman-Birge-Hopfield（LBH）带系统（125-250 nm）的强度比，两者都是光学禁戒发射。O/N2柱密度比是从地球轨道卫星（如GOLD（全球范围的翼盘观测））了解所有地磁条件下全球范围电离层和热层组成变化的关键。 该团队在上一个资助期的研究表明，过去50年的实验室光谱学未能测量级联诱导的紫外光谱，并确定LBH振动强度或级联发射横截面，这占总发射横截面的约30%，地球最强的FUV发射。由于陆地气辉观测和前向模型计算之间的二分法，这一失败在文献中引发了持续了十多年的争议。项目组在实验室中测量了由30-200 eV电子激发的N2的LBH带系统的FUV级联诱导光谱。级联跃迁开始于两个过程：辐射和碰撞诱导的电子跃迁（CIQs），涉及两个状态（a和w），随后是级联诱导跃迁a X。 在这个项目中，该团队将研究10-30 eV的阈值发射截面。 该项目的独特之处在于测量了原子O和分子N2的绝对Qem（总发射截面）和Qcasc（叶栅诱导截面）更准确地与一个特殊的设备设计了一个十倍大的碰撞室比以前的实验室测量，以适当地考虑级联的贡献在相同的实验条件下。实验室光谱学在LASP取得了里程碑式的一步，首次测量了N2的光禁戒级联诱导紫外光谱。 然而，需要做大量的工作来完成LBH和其他重要的光学禁戒跃迁，开始在第一个腔室（0.75米半径）的研究。 第二个腔室的半径为2米（是第一个腔室的两倍多），这使得原子和分子物理学进入了一个全新的领域。在过去的50年里，单散射电子碰撞诱导荧光光谱实验室研究可用的寿命范围为1- 100 ns（主要允许紫外电子跃迁）。利用科罗拉多大学的两个大型真空室，可以研究寿命为10 ms的更高禁戒跃迁，以捕获100 ms的全部光发射和部分光发射，并能够建模到1000 ms。 这一新的物理学领域涉及光禁戒跃迁，允许研究以前从未在单散射条件下测量过的光谱，如LBH、CO的卡梅隆带和N2的Vegard-Kaplan带系统。该提案的PI在测量地球和行星大气层感兴趣的原子和分子的绝对Qem和Qcasc方面有着广泛的50年跟踪记录。实验和建模的多方面方法都承诺一个关键的热层参数（O/N2）的理解地球的热层，并扩大范围到其他行星的大气。项目组的数据为当前和未来的卫星任务（例如，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Laboratory Study of the Cameron Bands, the First Negative Bands, and Fourth Positive Bands in the Middle Ultraviolet 180–280 nm by Electron Impact Upon CO

通过 CO 上的电子碰撞对中紫外 180–280 nm 中的卡梅伦能带、第一负能带和第四正能带进行实验室研究

• DOI: 10.1029/2020je006602
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Planets
• 作者: Lee, Rena A.;Ajello, Joseph M.;Malone, Charles P.;Evans, J. Scott;Veibell, Victoir;Holsclaw, Gregory M.;McClintock, William E.;Hoskins, Alan C.;Jain, Sonal;Gérard, Jean‐Claude
• 通讯作者: Gérard, Jean‐Claude

Laboratory Study of the Cameron Bands and UV Doublet in the Middle Ultraviolet 180–300 nm by Electron Impact upon CO 2 with Application to Mars

通过电子撞击 CO 2 并应用于火星对中紫外 180–300 nm 中卡梅伦谱带和 UV 双峰的实验室研究

• DOI: 10.3847/1538-4357/ac88c8
• 发表时间: 2022
• 期刊: The Astrophysical Journal
• 作者: Lee, Rena A.;Ajello, Joseph M.;Malone, Charles P.;Evans, J. Scott;Veibell, Victoir;Holsclaw, Gregory M.;McClintock, William E.;Hoskins, Alan C.;Jain, Sonal K.;Gérard, Jean-Claude
• 通讯作者: Gérard, Jean-Claude