Optogalvanic Detection of Laser-Desorbed Silver in a Low-Pressure Argon Atmosphere

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.