Femtosecond; Laser repetition rate; Limit of detection;INDUCED BREAKDOWN SPECTROSCOPY; NANOSECOND

Experimentally investigated limit of detection Mg, Al, Sr, Pb. depending on the pulse repetition rate femtosecond Ti: Sa laser optical breakdown in aqueous solutions on the surface of the investigated element in the laser pulse duration 60 fs, pulse energy of 1 mJ. The study was conducted for the laser pulse repetition rate of 50 Hz, 150 Hz, 250 Hz. To choose the optimal time delay of registration relative to the laser beam for the following chemicals:: Na, N, Fe, Ca, Mg, Al, Pb, Mn.

LIBS; high pressure; fuel-air ratio; ultrafast LIBS;

Application of time-resolved ultrashort-pulse-laser-based laser-induced breakdown spectroscopy (LIBS) is proposed for diagnostics in hydrocarbon flames at elevated pressures. Earlier study in nanosecond-laser-based LIBS for measuring fuel-to-air (F/A) ratios in stable hydrocarbon flame at high pressures is reported to have high measurement instabilities. A correlated measurement of time-resolved LIBS and electron number density measurement is carried out to develop an understanding of the source of the aforesaid measurement instability. The planned correlated measurements of LIBS and electron number density with short picosecond to femtosecond excitations have potentials to significantly reduce the instability in F/A ratio measurements at high pressure.