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Laser induced tropospheric ozone control

Kortsalioudakis Nathanail, Moustaizis Stavros, Tzortzakis Stelios

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Summary

A novel idea of controlling the ozone concentration in the troposphere by applying ultraviolet short laser pulses is proposed. The study involved: i) one experimental scheme of nanosecond pulses at 308 nm used for system calibration purposes and ii) two experimental schemes of femtosecond pulses at 248 nm by altering the conditions of beam propagation: a) linear (unfilamented) propagation and b) nonlinear (filamented) propagation. All schemes were performed in an ozone enriched atmospheric air environment under standard conditions of air pressure, temperature and humidity. The results showed ozone photolysis by femtosecond laser pulses at 248 nm is occurring about 7 times faster compared to the nanosecond pulses at 308 nm using same experimental conditions and energy amount per pulse. In addition the results are in a very good agreement both at 308 nm and 248 nm between predicted and experimental values within an uncertainty of 5% and 11% respectively. Finally the study of ozone photolysis by femtosecond pulses at 248 nm revealed a 25% faster time on ozone decomposition for the filamented scheme in comparison to the unfilamented one. This effect is believed to be due to the presence of electron density produced during the filaments formation, which accelerate the decomposition of ozone molecules by the electron impact collisions, while in the unfilamented case where only photolysis is occurred the electron density is negligible. These results allow us to propose a new method based on the nonlinear propagation of ultrashort laser pulses under filamentation formation for tropospheric ozone control.

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