Complex Robert-Bonamy Calculations of Pressure-Induced Shifts and Pressure-Broadened Halfwidths of Atmospheric Asymmetric Rotor Molecules

该项目涉及建立一个理论框架，以计算地球大气中痕量气体的压力加宽半宽和压力引起的谱线偏移。半宽度是减少遥感数据误差的主要来源，也是计算温室气体辐射强迫的逐线模型的主要误差来源。最近的工作还表明，在剖面检索中加入线位移减少了程序中的错误。为了解决这些问题，需要数千个振转跃迁的数据。因此，需要一个理论模型，计算效率高，能够准确地确定这些参数。复杂的Robert-Bonamy（CRB）形式主义是理论方法的基础。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。初步计算将做的物种，有几个振动带的实验测量进行比较。这些是被氮分子扰乱的水和臭氧。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。该项目由大气化学和实验物理化学计划共同支持。

This project involves the development of a theoretical framework to calculate pressure--broadened halfwidths and pressure-induced line shifts for trace gases in the terrestrial atmosphere. The halfwidth is the major source of error reducing remote sensing data and in line-by-line models used to calculate radiative forcing from greenhouse gases. Recent work also shows that the inclusion of the line shift in profile retrievals reduces the error in the procedure. To address these problems, data is needed for thousands of ro-vibrational transitions. Hence a theoretical model is needed that is computationally efficient and capable of determining these 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 halfwidth and line shift will be studied. The intermolecular potential and the dependence of the halfwidth 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 for several vibrational bands to compare with. These are water and ozone perturbed by molecular nitrogen. 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 project is supported jointly by the Atmospheric Chemistry and the Experimental Physical Chemistry Programs.