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（压力加宽的半宽度和压力引起的谱线偏移）建立一个理论框架。 需要精确的半宽度来解释遥感数据和用于计算温室气体辐射强迫的逐线模型。 在轮廓检索中包括线偏移也减少了这些检索中的错误。 需要数千个振转跃迁的数据。 需要一个理论模型，计算效率高，能够准确地确定所需的参数。复杂的Robert-Bonamy（CRB）形式主义的理论方法的基础。 计算使用现实的分子动力学，在相互作用势的所有相关条款，没有截止程序。 将研究显式速度平均对半宽和线位移的影响。 分子间的潜力和依赖的半宽度和线位移的参数描述这种潜力将被调查。 将通过非线性最小二乘拟合实验和理论数据来优化电位。 初步计算将进行的物种，有实验测量的两个参数的几个振动带进行比较，如水和臭氧分子的氮和氧的扰动。 该理论也将被扩展到考虑这些物种的自加宽和移动以及波函数的其他发展。 这些碰撞引起的参数的振动状态，转动状态和温度依赖性将被调查。 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。 将为本科生提供研究经验。 该奖项由大气化学计划（大气科学部/地球科学局）和实验物理化学计划（化学部/数学和物理科学局）共同支持。

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).