Atmospheric NO3 free radical concentration measurement system based on double-cavity type cavity ring-down technology

Abstract

The invention discloses an atmospheric NO3 free radical concentration measurement system based on a double-cavity type cavity ring-down technology. The measurement system utilizes two ring-down cavities to simultaneously measure the ring-down time and the background ring-down time, and includes a function generator, a diode laser device, an optical isolator, a first ring-down cavity, a second ring-down cavity, a narrowband color filter, a photoelectric detector and a capture card. The external-modulation diode laser device outputs a pulse laser, the pulse laser passes through the optical isolator and then is divided into two beams by a beam splitter, the two beams of pulse lasers respectively go into the first ring-down cavity and the second ring-down cavity, and the two ring-down cavities are in rear-connection with the photoelectric detector. The NO3 free radical ring-down time is extracted from an obtained ring-down signal acquired by the first ring-down cavity; and at the same time, the NO3 free radical background ring-down time is extracted from the ring-down time obtained by the second ring-down cavity. Under the condition of a known NO3 free radical absorption cross section sigma, the NO3 free radical concentration is obtained by calculation through the following formula as described in the specification, where RL and c are constants.

Description

technical field [0001] The present invention relates to atmospheric NO 3 The field of free radical detection system is specifically an atmospheric NO3 free radical concentration measurement system based on dual-cavity cavity ring-down technology of modulated diode laser. Background technique [0002] NO 3 Free radicals are the most important oxidants in the nocturnal atmosphere, measuring NO in the nocturnal atmosphere 3 The concentration of free radicals is a prerequisite for the study of nighttime atmospheric chemistry. At present, the main measurement methods are matrix-isolated electron paramagnetic resonance spectroscopy (MI-ESR) technology, laser-induced fluorescence (LIF) technology, and differential absorption spectroscopy (DOAS) technology. Among them, MI-ESR technology is to isolate the matrix Technology combined with electron paramagnetic resonance technology to measure highly chemically active free radicals requires low-temperature capture of air samples for l...

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However, because YAG lasers are generally used to pump dye lasers as pulsed light sources, they are bulky, expensiv

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