Monitoring Chemical Reactions Induced by Filamentation with Air-Lasing-Based Coherent Raman Spectroscopy

Simultaneous detection of multiple reaction products induced by filamentation is crucial for unraveling complex atmospheric chemistry but remains challenging technically. Herein, we employ air-lasing-based coherent Raman spectroscopy to simultaneously monitor the formation and evolution of O3 and NO2 after femtosecond laser filamentation in synthetic air. Simultaneous detection of the two species reveals their distinct reaction dynamics. Experimental results show that the dynamical evolutions and accumulated concentrations of O3 and NO2 strongly depend on pump energy and reaction environment. The decreasing pump energy slows chemical reactions due to reduced reactive species concentrations. Lower energies promote O3 accumulation, whereas the production of NO2 require higher energies. Moreover, the O3 signal disappears in ambient air, while the NO2 signal in ambient air differs slightly from that in synthetic air after a sufficient reaction time. The analysis of reaction pathways qualitatively explains the experimental results. This study provides guidance for control over atmospheric chemical reactions.