Laser induced aerosol formation mediated by resonant excitation of volatile organic compounds

Abstract

Since its first demonstration, laser induced aerosol formation (LIAF) has been studied in various environmental conditions and laser parameters. LIAF driven by UV and near-IR lasers mainly relies on the nitrogen photo-oxidative chemistry, leading to the production of hygroscopic H N O 3 , which stabilizes the growth of aerosol nanoparticles. Mid-IR lasers were expected to be drastically less effective for LIAF, due to their much lower multiphoton photodissociation and ionization rates. Here, we report on the observation of surprisingly high yields of nanometric and sub-µm aerosol formation driven by mid-IR laser pulses, which cannot be explained by the H N O 3 -pathway. We hereby evidence a new mechanism of aerosol stabilization and growth, based on the resonant excitation of volatile organic compounds (VOCs) by mid-IR pulses whose spectrum is broadened during filamentation.