汽油、柴油燃料的挥发及城市机动车等尾气排放存在大量的烷烃、环状烷烃及氮氧化合物，随后通过燃烧、紫外线光照等一系列的化学反应，导致大气光化学烟雾和酸雨等严重的环境问题，极大地损害人和动物的健康、影响植物生长、降低大气的能见度、加速橡胶制品老化和腐蚀建筑物等等。本论文主要通过脉冲直流放电和激光诱导荧光技术直接有效监测自由基含量、存在寿命、光谱特征等，从而清楚地了解自由基的结构、热力学及动力学性质，为进一步改善或者减少大气污染物排放提出解决方案。本论文主要包括三个方面的工作。第一，搭建了超声射流放电发射谱及激光诱导荧光光谱实验装置，开发了基于labVIEW 2009的高压直流脉冲放电发射谱和激光诱导荧光光谱软件平台，实现了荧光数据实时采集、数据实时处理、监测个体仪器运行状态及图谱打印等功能。第二，获得了超声射流脉冲直流氮气放电发射谱，研究了 活性态(0，0)带(λ=337.0nm)和 活性态(0，0)带（λ=391.4nm）发射强度受低真空压力（5-130Pa）和脉冲放电电压（3000-6300 V）的影响，并给出了我们实验条件下直流放电过程中电子碰撞机理并作出相应的解释。第三，首次在实验中获得了超声射流条件下1-甲基环己烷氧自由基和2-环己基乙烷氧自由基的振动分辨的激光诱导荧光（LIF）光谱，借助量子化学理论计算B3LYP/6-31+G(d)和CASSCF/6-31+G(d)等方法，对得到的LIF激发谱进行分析与图谱解析。同时，借助理论计算讨论了环己基的取代基距离烷氧碳位置不同时分子解离、异构或分子内转动等竞争反应导致实验光谱中未出现v>1 C-O伸缩振动序列的原因。

Air pollution is a major environmental problem worldwide. Cyclohexoxy radicals and NOx are important participators in the atmospheric chemistry, and hence attract intensive attention from researchers. Spectroscopic and conformational studies can provide convenient methods to monitor these species and help to understand the reaction mechanism in the atmosphere. In this thesis, pulsed DC discharge spectroscopy and laser-induced fluorescence (LIF) spectroscopy are used to study the products of nitrogen in the discharge and cyclohexoxy radicals in the supersonic jet. The reaction mechanisms on the excited states of these species are investigated and the correspondence between the spectrum and the conformational structure is discussed. The main content can be summarized as below:(1) We developed the hardware and software systems of the supersonic free-jet discharge emission spectroscopy and LIF spectroscopy based on LabVIEW 2009. The software system achieved synchronous control of equipments, acquisition of real-time fluorescence data, and communicating with the computer via GPIB, USB, RS232, and parallel ports. The system can also accomplish data display, saving, analysis, and printing.(2) The population of nitrogen and states in a pulsed direct current (DC) discharge supersonic free-jet are monitored by recording the emission intensities of the (0-0) band (λ=337.0nm) of the 2nd positive system and the (0-0) band (λ=391.4 nm) of the 1st negative system. Different pressure dependence phenomena are observed within the 5-130 Pa pressure range and possible excitation mechanisms under experimental condition are proposed. Influence of the discharge voltage(3000-6300 V) on the intensities is also studied. (3) The LIF spectra of 1-methylcyclohexoxy and 2-cyclohexylethoxy radicals were obtained first time in the supersonic jet condition. For 1-methylcyclohexoxy, a tertiary ring alkoxy radical, the spectrum was assigned preliminarily to the chair-axial and chair-equatorial conformers of 1-methylcyclohexoxy. No C-O stretch progression was observed in 1-methylcyclohexoxy spectrum which was different from t-butoxy. Short lifetime of excited state 1-methylcyclohexoxy and increased C-O bond length suggested a less stable excited state induced by the increased steric repulsion via methyl substitution on the alkoxy carbon. Dissociation rather than H transfer was suggested as the major nonradiative relaxation process which competed with the fluorescence path. For 2-cyclohexylethoxy, the spectrum was also assigned to specific conformers of the radicals assisted by theoretical calculations using B3LYP/6-31+G(d) and CASSCF/6-31+G(d) methods. The results will contribute to the fundamental chemical and structure investigation of ring compound.