中文摘要：

NO3自由基是夜间大气中最重要的氧化基团，鉴于NO3自由基易变性以及极低的大气浓度，开发了以发红光二极管（LEDs）为光源来监测大气NQ自由基的长程差分吸收光谱系统（LEDs—DOAS）。分析了新型红光二极管Luxeon LXHL-MD1D LEDs的谱特性，研究了以其为光源的长程LEDs-DOAS系统测量大气NO3自由基的原理，设计了大气NO3测量自由基的装置，给出监测的大气吸收光谱，研究了反演NO3的方法，并给出反演谱图和一周大气NO3浓度的时间序列图。研究结果表明当光程为2．8km时，LEDs-DOAS系统的探测限大约为12ppt。

英文摘要：

Nitrate radical （NO3） is the most important oxidant in the tropospheric nighttime chemistry. Due to its high reactivity and low atmospheric concentrations, modem red light emitting diodes （LEDs） was proposed as light source in long path differen- tial optical absorption spectroscopy （LP-DOAS） to measure NO3 radical in the atmosphere. The spectral properties of Luxeon LXHL-MD1D LEDs were analyzed in the present paper. The principle of LEDs-DOAS system to measure nitrate radical was studied in this paper. The experimental setup and retrieval method of NO3 radical were discussed in this paper. The retrieved ex- ample of NO3 was given and the time series of NO3 concentrations was performed for a week. The results showed that the detec-tion limits of LEDs-DOAS system were 12 ppt for atmospheric NO3 radical when the optical path of LEDs-DOAS system was 2. 8 km.