Ab Initio方法研究NO分子红外光谱参数

分子光谱参数是红外辐射计算的基础数据,目前国内还没有类似HITRAN数据库的气体光谱数据库,在国家数值风洞工程的支持下,本文开发了高温空气光谱参数计算代码,目的是为目标红外辐射计算提供支持。NO是高超声速飞行器高温空气流场中的主要化学反应产物之一,其振转能级跃迁产生的辐射处于红外探测器的典型波段。本文基于ab initio计算的NO分子分裂后的分子势和永久偶极矩,计算了NO分子的线强度(温度达到了8000 K);在300 K和3000 K温度下,目前的理论计算结果与HITRAN数据库中的数据符合得非常好;本文还采用窄带模型计算了296 K和2000 K温度下NO分子X²Π_1/2态的吸收系数。目前所用方法可以不借助实验光谱常数,使低振动态和高振动态都得到比HITRAN数据库更多的线位置,可为国家数值风洞目标辐射特性计算提供NO分子高温光谱数据。

Study on IR Spectral Parameters of NO by Ab Initio Method

Molecular spectral parameters are fundamental data for IR radiation calculation.Currently,there is no such gas spectral database as the high resolution transmission molecular absorption database(HITRAN database)in China.In this paper,supported by the National Numerical Windtunnel(NNW)project,we developed the calculation codes of high-temperature air spectral parameters to support the calculation of target IR radiation.To be specific,NO is one of the products of chemical reactions in the high-temperature air flow field of hypersonic vehicles,and the radiation generated by its vibration-rotation levels is in the typical band of infrared detectors.Based on the molecular potential and permanent dipole moment of split NO calculated by the ab initio method,we calculated the line intensity of NO at 8000 K,and the theoretical calculation results were in a good agreement with the values from the HITRAN database at 300 K and 3000 K.Moreover,we calculated the absorption coefficient of NO at the X²Π_1/2 state at 296 K and 2000 K by employing the narrow-band model.It turns out that without the help of experimental spectral constants,the proposed method can obtain more line positions than the HITRAN database in both low and high vibration levels,which can provide the high-temperature spectral data of NO for the calculation of target radiation characteristics in the NNW project.