Abstract

We report the first detailed investigation of laser-desorbed material probed by laser optogalvanic spectroscopy. When Ar transitions in the 555-575 nm region are excited, the laser-desorbed silver optogalvanic effect (OGE) temporal signal appears as a shoulder on the Ar OGE peak. Our studies show that the shoulder is due to Penning ionization of laser-desorbed Ag by Ar in highly excited states (15.12-15.51 eV). The temporal dependence of the laser desorption process was investigated. It was found that most of the sample was desorbed within, at most, 1200 laser pulses (2 min). A crude estimate of the absolute detection limit obtained here is tens to hundreds of nanograms; use of a dedicated, custom apparatus rather than the commercial, shielded hollow cathode lamp used in this study should permit confirmation of and improvement on this detection limit. The presence of a low-pressure argon atmosphere and the use of moderate laser power density may be crucial for successful application of this technique.

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