Time resolved laser induced breakdown spectroscopy for fluorine, chlorine and sulfur detection using an optical fiber probe

Our goal is to develop an optical spectroscopy analysis of toxic molecular compounds by using the atomic emission of a plasma induced by a Nd:YAG lase r (TRELIBS). The qualitative and quantitative analysis have been carried ou t on chlorine and fluorine atoms from organohalogenated molecules. The expe rimental setup uses a Nd:YAC laser at 1064 nm and a cylindrical cell in sta inless steel through which the gas flow is introduced. The laser beam is fo cused in the cell through a BK7 lens, while the emission wavelengths are an alyzed by a 24 optical fiber probe connected to a spectrometer with an opti cal multichannel analyzer, and a computer. The time resolution of plasma em issions with a gated image intensifier leads us to a best signal to noise r atio (SNR) on atomic emission lines with 0.5 to 4 mu s delay between the en d of the laser pulse and the detector aperture. Spectral, time and space re solution permit a high reproducibility and a good sensitivity of the method (close to 10 ppm(w/w)). The high temperature of the plasma produced by a laser beam of 100 mJ is re sponsible of the total decomposition of the molecular structure and explain s the high excitation states of the atoms such as Cl, F, S, P.