NO_2分子内能传递和弛豫过程的光声和荧光光谱探测  

Investigation on Internal Energy Transfer and Relaxation Kinetics of NO_2 by Photoacoustic and Fluorescence Emission Spectra

作　　者：张贵银[1] 马金英[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》2011年第3期742-745,共4页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(10647130)资助

摘　　要：将荧光光谱和光声光谱两种互补的探测技术结合起来,从辐射和无辐射跃迁两个方面,分析了532nm激光作用下,NO2分子的激发和弛豫过程。发现NO2分子在激光作用下,将跃迁至第一激发电子态,当样品气压较低时,受激NO2分子除辐射荧光外,可通过快速的内能转移过程实现在几个振转能级的再布居;随样品气压的升高,分子间碰撞加剧,受激NO2分子通过分子间的碰撞,实现在多个振转能级的再布居。激光布居能级的荧光辐射效率随样品气压的升高逐渐降低,而长波区域的荧光辐射及光声信号强度逐渐增强,说明在高样品气压条件下,受激NO2分子的弛豫过程除辐射荧光外,还存在很强的碰撞弛豫过程,在碰撞弛豫过程中受激NO2分子将振动能转化为热运动的平动能,引起温度升高而产生很强的声信号。With 532 nm laser as excitation source,the excitation and relaxation process of NO2 molecule was investigated by the technique of photoacoustic and fluorescence emission spectra.The results show that NO2 molecules will be pumped to the first excited electronic state by laser photon.When the sample pressure is lower,some of the excited molecules relax to the ground state by radiation process directly;the other parts are redistributed to a few of the excited rovibronic energy levels by the process of fast internal energy transfer.With the increase in the sample pressure,continual collisions dominate the relaxation process gradually.This makes the excited molecules to be redistributed to many excited rovibronic energy levels.Emission from these excited levels forms a continuous spectrum.Just then,the efficiency of fluorescence emission from laser excited level decreases and the fluorescence intensity on the long wavelength side increases.The intensity of PA signals increases also.These phenomena indicate that besides the relaxation process of radiation,there is a strong relaxation process of continual collision under the condition of higher sample pressure.It converts vibration energy of the excited molecules into translation one.This induces the increase in gas temperature and a sound wave is produced.

关 键 词：分子光谱 荧光光谱 光声光谱 NO2分子 弛豫 

分 类 号：O433.4[机械工程—光学工程]