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...

AI Technical Summary

Problems solved by technology

However, because YAG lasers are generally used to pump dye lasers as pulsed light sources, they are bulky, expensive, difficult to maintain, and are not conducive to miniaturization, making it difficult to develop into instruments.

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