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.