Line Shape for Water Vapor and Other Atmospheric Asymmetric Rotor Molecules

该项目涉及为计算地球大气中痕量气体的光谱参数（压力加宽半宽度和压力引起的线移）建立一个理论框架。为了解释遥感数据和用于计算温室气体辐射强迫的逐行模式，需要精确的半宽度。在概要文件检索中包含行移位也减少了这些检索中的错误。需要数千个非振动跃迁的数据。需要一种计算效率高、能够准确确定所需参数的理论模型。复杂的Robert-Bonamy （CRB）形式主义是这一理论方法的基础。计算使用实际分子动力学，相互作用势中的所有相关项，并且没有截止程序。研究显式平均速度对半宽和线移的影响。分子间势和半宽度和线移对描述该势的参数的依赖关系将被研究。通过非线性最小二乘拟合对实验和理论数据进行优化。最初的计算将对那些有几个振动带的两个参数的实验测量值可供比较的物种进行，例如受氮分子和氧分子扰动的水和臭氧。该理论还将扩展到考虑这些物种的自展宽和移动以及波函数的其他发展。这些碰撞诱发参数的振动状态、旋转状态和温度依赖性将被研究。这项工作将提高我们对光谱遥感结果的信心，并使我们能够更好地确定温室气体的辐射强迫。为本科生提供研究经验。该奖项由大气化学项目（大气科学部/地球科学理事会）和实验物理化学项目（化学部/数学和物理科学理事会）联合支持。

This project involves developing a theoretical framework for calculating spectroscopic parameters (pressure-broadened half-widths and pressure-induced line shifts) for trace gases in the terrestrial atmosphere. Accurate half-widths are needed for interpreting remote sensing data and in line- by-line models used to calculate radiative forcing from greenhouse gases. The inclusion of the line shift in profile retrievals also reduces errors in these retrievals. Data for thousands of ro-vibrational transitions are needed. A theoretical model is needed that is computationally efficient and capable of determining the desired parameters accurately.The complex Robert-Bonamy (CRB) formalism is the basis of the theoretical approach. The calculations use realistic molecular dynamics, all relevant terms in the interaction potential, and no cutoff procedure. The effects of explicit velocity averaging on the half-width and line shift will be studied. The intermolecular potential and the dependence of the half-width and line shift on the parameters describing this potential will be investigated. The potentials will be optimized by nonlinear least-squares fits to experimental and theoretical data. Initial calculations will be done for species for which there are experimental measurements of both parameters for several vibrational bands to compare with, such as water and ozone perturbed by molecular nitrogen and oxygen. The theory will also be extended to consider self-broadening and shifting of these species and other developments of the wavefunctions. The vibrational state, rotational state, and temperature dependence of these collision-induced parameters will be investigated. This work will improve our confidence in spectroscopic remote sensing results and allow a better determination of the radiative forcing of greenhouse gases. Research experiences for undergraduate students will be provided. This award is supported jointly by the Atmospheric Chemistry Program (Division of Atmospheric Sciences/Directorate of Geosciences) and Experimental Physical Chemistry Program (Division of Chemistry/Directorate of Mathematical and Physical Sciences).