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

该项目涉及一个理论框架的发展，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线移。在用于计算温室气体辐射强迫的逐行模式中，半宽度是减少遥感数据误差的主要来源。最近的研究还表明，在剖面检索中包含线移可以减少过程中的误差。为了解决这些问题，需要数千个无振动跃迁的数据。因此，需要一种计算效率高、能够准确确定这些参数的理论模型。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。将研究分子间势以及描述该势的参数与半宽和线移的关系。通过非线性最小二乘拟合对实验和理论数据进行优化。对于有几个振动带的实验测量值可供比较的物种，将进行初步计算。这些是受氮分子干扰的水和臭氧。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。本项目由大气化学和实验物理化学联合资助。

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.