Femtosecond laser filamentation for sensing combustion intermediates: A comparative study

We demonstrate experimental evidences that femtosecond filament-induced clean fingerprint fluorescence can indeed be employed to characterize the combustion intermediates in flames. By comparing the emission spectra obtained from an ethanol-air flame by femtosecond filament excitation, nanosecond laser-breakdown excitation, as well as without any laser excitation, it is found that the filament-induced fluorescence in the combustion flame mainly results from the interaction of femtosecond laser pulses with the combustion intermediates such as OH, CH, and C2 existing in the combustion, but not from the fragmentation of parent ethanol molecules. © 2014 Elsevier B.V.