Laser-induced breakdown spectroscopy: Time-resolved spectrochemical applications

We have added time resolution to laser-induced breakdown spectroscopy in two forms, by gating an optical multichannel analyzer (OMA) and by time-resolving the output of a photomultiplier with a boxcar amplifier. Spectra were obtained for temporal segments of 25 to 100 ns, from 25 ns to 50 µs after initiation of the breakdown. OMA spectra of oxygen illustrate the power of this technique for survey purposes. The photomultiplier-boxcar arrangement was used to detect phosphorus atoms from diisopropylmethyl phosphonate in air, and also to detect chlorine in air, both in real time. In the former experiments we detected 690 ppm (w/w) of phosphorus and project a limit of detection with our current apparatus of 15 ppm (w/w). For chlorine, we observed signal from 120 ppm (w/w) and project a limit of detection of 60 ppm (w/w).