中文摘要：

研究了一种应用于气体扩张激光诱导荧光（FAGE）技术测量OH自由基的染料激光器波长修正方法。该方法采用镍铝丝热解水汽产生稳定的高浓度OH自由基,利用重复频率为8500 Hz的染料激光器输出波长约282 nm激光作为光源.激发低压腔内热解产生的高浓度高稳定性OH自由基产生荧光,由普通光电倍增管和光电二极管分别探测激发荧光和出腔激光强度。通过延时信号发生器统一触发激光器和高速数据采集卡并结合LabVIEW软件处理得到单位激光强度的荧光积分强度数据。连续两次扫描激光波长,当第二次扫描的荧光积分强度达到第一次最大值的0.95倍时,停止波长扫描,此时的激光器波长位置即为激发线位置。本文首先扫描激光波长,研究了282 nm激发机制下的OH自由基激发谱;然后在Q_1 2激发线位置探究了气体湿度、氧气含量、进气量以及抽速对荧光积分强度和寿命的影响;并分析了镍铝丝热解水的反应机理,初步认为热解中OH自由基主要来源于氧原子与水的反应。在以上荧光积分强度和寿命影响因素的研究基础上,优化了系统参数,使荧光积分强度波动小于±1.9%。连续多次进行波长修正,修正偏差为0.1pm。该方法能够满足气体扩张激光诱导荧光（FAGE）技术定量精确测量大气OH自由基对波长的要求。

英文摘要：

A method for dye laser wavelength correction applied for the measurement of OH radical with FAGE（Fluorescence Assay by Gas Expansion） is researched in this article.Sufficiently stable concentration of OH radical is produced with thermal dissociation of H_2O by using an alumel filament and the fluorescence is excited with 282 nm laser in a low pressure cell.The fluorescence is detected with a photomultiplier and a high speed data acquisition card,while the laser light is monitored by a photodiode,and both signals are handled by a LabVIEW program for further analysis.The data acquisition card is triggered by a positive TTL pulse generated by a digital delay generator,which is triggered by a rising edge of a synchronized output pulse of the dye laser.The LabVIEW program is used to determine the location of the OH excited line according to the fluorescence intensity of OH radical when the frequency of the dye laser is scanned.By scanning dye laser wavelength range in 281.97～282.28 nm,excitation spectrum of OH radical is recorded.In order to optimize system parameters and achieve a high signal-to-noise ratio,the effects of the humidity,oxygen concentration,mass flow and pumping speed on fluorescence intensity and lifetime are studied at Q_1 2 line and less than ±1.9%fluctuations of the fluorescence intensity is obtained.With analysis of the reaction mechanism of the thermal dissociation of H_2O,it is concluded that reaction of oxygen and water is a major source of OH radical.Laser output wavelength is scanned in a small range around Q_1 2 line to find out the exact exciting line and then correct the laser＇s output,which might slightly shift due to the environmental change and leads to reduction of fluorescence intensity.The wavelength correction procedure is implemented many times and the results show that the systematic error of the instrument is less than 0.1pm.According to the experimental results,this method meets the needs of quantitative accurate measuring tropospheric OH radical by FAGE.