飞秒激光成丝诱导分子光谱方法及其在环境检测中的应用研究

Since the spectrum technique of fluorescence induced by femtosecond laser filamentation has high spatial (several tens of microns) and temporal (picosecond magnitude) resolution, and can effectively detect various components at the same time, it is of great importance for the diagnosis of combustion and plasma process containing free radicals with short lifetime. In this project, we attempt to control the filament shape by adjusting the laser parameters, adjust the filament length by introducing chirped Bessel-gaussian beam and change the filament lifetime by adopting double (multiple) pulse technique, so as to conduct the research on the fluorescence spectral of molecules (oxysulfide, oxynitride, oxycarbide and other pollutant molecules in atmosphere) induced by the femtosecond laser filamentation, and get deeper insight into the mechanism of interaction of ultrashort laser pulses with atoms and molecules, and the molecular structure and radiation characteristics in plasma environment. In addition, we will investigate the mechanism of fluorescence emission of these molecules and the influence of gas flow, temperature, gas pressure, relative humidity and other meteorological parameters on the fluorescence emission, explore the way to enhance fluorescence emission and improve the detection sensitivity, getting deeper insight into the mechanism of the interaction of ultrashort laser pulses with atoms and molecules. On this basis, we utilize the filament-induced fluorescence to detect the pollutants in real atmospheric environment and during the combustion of fossil fuels, obtaining its composition and space-time distribution, which lays the foundation for the development of laser induced fluorescence detection technique to quantitatively analyze the composition of various pollutants in atmospheric environment simultaneously.

飞秒激光成丝诱导荧光光谱技术具有很高的空间（几十微米）和时间（皮秒量级）分辨能力，而且能同时有效地完成对多种成分探测，这对诊断存在短寿命自由基的燃烧和等离子体过程极为重要。本项目提出通过调节激光参数来控制丝的形态，引入初始啁啾的贝塞尔-高斯整形光束控制丝的长度，同时采用双(多)脉冲技术的方法改变丝的寿命，开展对飞秒激光脉冲成丝诱导分子(硫氧化物、氮氧化物、碳氧化物等大气污染物分子)产生的荧光光谱研究，深入地了解超短激光脉冲与原子分子相互作用机制和等离子体环境中的分子结构和辐射特性。此外，我们将研究这些分子荧光发射机制以及气体流动、气温、气压等气象参数对荧光发射的影响，探求增强荧光发射并提高探测灵敏度的途径。在此基础上利用成丝诱导荧光对真实大气环境中以及化石燃料的燃烧过程中的污染物进行检测，获得其成分和时空分布等信息，为发展能够同时定量分析环境中污染物成分的成丝诱导荧光技术奠定基础。

飞秒激光成丝诱导荧光光谱技术具有很高的空间（几十微米）和时间（ps量级）分辨能力，而且能同时有效地完成对多种成分探测，这对诊断存在短寿命自由基的燃烧和等离子体过程极为重要。这一特点为实时、高效、精准、安全、环保地监测大气环境提供了极好的平台。在本项目中，我们主要开展了以下研究：1. 研究了飞秒激光脉冲在含有微量污染物(如硫氧化物、氮氧化物、一氧化碳、苯类、烷类等分子)的空气中成丝过程，并探测成丝过程中的这些分子的荧光发射；2. 通过调节激光初始能量、脉宽、束腰、偏振特性、啁啾等参数，采用贝塞尔-高斯光束、双(多)脉冲技术寻求对控制丝的长度、寿命以及形态的最佳方案; 3. 研究一氧化碳、苯类、烷类等分子荧光发射机制以及气体流动、气温、气压等气象参数对其荧光发射的影响，发现了几种增强荧光发射并提高探测灵敏度的途径；4. 发展了分析和处理光谱数据的方法，实现提高数据精度并计算等离子体密度、电子温度等参量的功能。通过这些研究，我们深入地了解超短激光脉冲与原子分子相互作用机制和等离子体环境中的分子结构和辐射特性，并在此基础上利用成丝诱导荧光对真实大气环境中以及化石燃料的燃烧过程中的污染物进行检测，获得其成分和时空分布等信息。这一研究为发展能够同时定量分析环境中污染物成分的成丝诱导荧光技术奠定基础。