NO_2分子荧光辐射的时间分辨谱  

Time Decay Spectrum of NO_2 Fluorescence Radiation

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》2008年第12期2900-2903,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：以Nd∶YAG脉冲激光器抽运的光学参量发生器/放大器作激发光源,采用激光诱导荧光光谱技术对NO2分子激发电子态的荧光辐射寿命进行了实验研究。结果显示,NO2分子的荧光辐射寿命与激发波长、样品气压密切相关。不同波长的激光激发NO2分子,激发电子态荧光辐射的时间分辨谱均以双指数规律衰减,荧光辐射由长、短两种寿命成分组成,短寿命成分产生于NO2分子A2B2和B2B1←X2A1激发跃迁的荧光辐射,而长寿命成分产生于NO2分子由X2A1向A2B2与X2A1耦合能级激发跃迁的荧光辐射。通过分析两种寿命成分随样品气压变化的机理,确定了产生短寿命荧光的受激分子主要通过辐射荧光和快速的内转换过程退激发;而产生长寿命荧光的受激分子除辐射荧光外,则主要通过碰撞无辐射跃迁过程退激发。Investigation of the optical absorption and fluorescence of NO2 molecule has long been of interest because it is not only one of the key substances of air pollution,but also a stable molecule of nonzero spin and has many special properties such as that the vibronic levels of the first excited state are coupled strongly to the high vibration levels of the ground state,so that once NO2 molecules are excited,they must undergo complicated quenching process.The quenching mechanism influences the lifetime of the excited molecule severely.In the present paper,the fluorescence lifetime of NO2 excited electronic states are observed experimentally by the technique of LIF time decay spectroscopy and with an optical parameter generator and amplifier pumped by a Nd∶YAG laser as excitation source.The results show that the fluorescence lifetime of excited NO2 molecules depends on the excitation wavelength and sample pressure.The time decay curves present a property of bi-exponential when the excitation wavelength is selected as 429.0,452.0,509.0 and 532.0 nm,respectively.This indicates that the fluorescence is composed of two components.One has a long lifetime,while the other has a short one.The short-lived component comes from the radiation of the molecules excited by A^2B2,B^2B1←X^2A1 transition.And the long one is owing to the radiation of the molecules excited to the high rovibronic levels of the ground electronic state.These levels are correlated with A2B2 state.The de-excitation mechanism of the excited molecules is investigated by measuring the variation in fluorescence lifetime versus the sample pressure.The conclusion is that the excited molecules corresponding to the short lifetime quench mainly through the process of radiation and fast inner conversion.As to the excited molecules with long lifetime,the de-excitation process is not only radiation,but also the non-radiation process of collision.

关 键 词：时间分辨谱 NO2 辐射寿命 退激发机制 

分 类 号：O433.4[机械工程—光学工程]