NO分子光声光谱的理论分析  

Theoretical Analysis of Photoacoustic Spectrum of NO Molecule

作　　者：张贵银[1] 靳一东[1] 

机构地区：[1]华北电力大学数理系,河北保定071003

出　　处：《光谱学与光谱分析》2010年第2期297-300,共4页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(10647130);华北电力大学博士科研基金项目(200612003)资助

摘　　要：采用拉普拉斯变换严格求解二能级系统光与物质相互作用的速率方程，获得了强激光诱导气体分子系统光声信号的解析表达式。结果显示光声信号的大小与样品分子的吸收截面、激发光强度、分子共振跃迁吸收的光子数、分子碰撞弛豫速率等因素有关。借助于光声信号随激光强度的变化关系，将NO分子在420.0～470.0 nm波长区间的激光诱导光声光谱归属于NO分子经X 2Π→A 2Σ的双光子激发跃迁及X 2Π→E 2Σ，F 2Σ，R 2Σ的三光子激发跃迁，由此获得NO分子A 2Σ，E 2Σ，F 2Σ和R 2Σ激发电子态的振动常数分别为2 346，2 342，2 397和2 381 cm-1，结果与采用其他方法测量的结果符合得较好。并对光声信号随缓冲气压升高而出现饱和的现象进行了理论解释。The technique of photoacoustic （PA） spectrum is based on the conversion of photon to acoustic energy by collision quenching of the excited molecules. It holds the characteristic of higher detection sensitivity, wide detection spectral region, no damage to the sample etc. It is used in many scientific observation areas such as gas composition analysis, research on chemistry and biology, environmental monitor and so on. In the present paper, the analytic formula of the PA signal produced from the in- teraction of intense laser with gas system was deduced by solving the dynamic rate equation about the interaction of photon and material. The results show that the magnitude of the PA signal depends on the factors of molecular absorption cross-section, la- ser intensity, photon number absorbed by the molecule and collision relaxation rate. With the aid of the relation of the PA signal versus laser intensity, the PA spectrum of NO molecule in the wavelength region of 420. 0-470. 0 nm is ascribed to the transition of X 2Π（v″=0）→A 2Σ（v′=0.1） and X 2Π（v″=0）→E 2,Σ（v＇=2, 3, 4）, F 2,Σ（v＇=1,2,3） and R Σ（v＇=0, 1）. These transi- tions are realized via two or three-photon process. The vibration constants of NO A 2Σ, A 2Σ, F 2Σ and R 2Σ electronic states were calculated from the wavelength of the spectral peaks. They are 2 346, 2 342, 2 397 and 2 381 cm 1 respectively. The re- sults are consistent with the one of other method. The phenomenon of saturation appears when the buffer gas pressure is high enough. This is owing to the finite excited molecules.

关 键 词：激光光谱学 光声光谱 二能级 NO 缓冲气体 

分 类 号：O433.5[机械工程—光学工程]