装置と技術

レーザー誘起蛍光法による大気中NO₃/N₂O₅測定装置

Analyzer for Measuring NO₃/N₂O₅ in the Atmosphere
by Laser-Induced Fluorescence Technique

松本　淳・小杉如央・今井秀和・梶井克純
Jun MATSUMOTO, Naohiro KOSUGI, Hidekazu IMAI,
and Yoshizumi KAJII

NO₃ and N₂O₅ are important as intermediates of NO_x loss in the nocturnal atmosphere. In this study, laser-induced fluorescence (LIF) technique is applied for measuring NO₃ and N₂O₅ in the atmosphere. A tunable dye laser pumped by a pulsed Nd:YVO₄ laser was utilized as an excitation light source. NO₃ was excited around its 623-nm absorption peak and the induced fluorescence was detected. For measuring N₂O₅, thermal decomposition of N₂O₅ was carried out and then generated NO₃ was detected. As a result of improvement and calibration of the instrument, the limits of detection for NO₃ and N₂O₅ reached 4 and 6 pptv, respectively (S/N = 1, 10-min averaging). A measurement test of N₂O₅ was conducted in the urban atmosphere to check the applicability of the instrument. The LIF instrument is promising to measure atmospheric NO₃ and N₂O₅. This is a successful case of applying a spectroscopic method to the environmental chemistry.

Keywords: LIF, Nitrate radical, Dinitrogen pentoxide, Calibration, Atmospheric chemistry