Investigations involving laser-based sampling of copper into an auxiliary pulsed glow discharge for ionization and excitation are presented. The interaction of the ablated copper with the auxiliary glow discharge was studied by monitoring the copper atom emission signal at 368.744 nm. Results demonstrate the ability to time ablation appropriately to access specific temporal regions of the pulsed plasma. More specifically, laser-ablated material was introduced into the glow discharge negative glow during the afterpeak. Ionization and excitation was accomplished by collisions with a metastable argon population produced by the glow discharge (Penning ionization) followed by recombination to yield excited-state Cu atoms. The work presented investigates parameters that affect the atomic emission signal intensity of the ablated material, including cathode-to-target distance, discharge gas pressure, and relative timing of discharge and ablation. Results demonstrate that decreasing the glow discharge working gas pressure increases the transport efficiency of laser-ablated material into the negative glow. These investigations are part of an ongoing series of studies on sample introduction schemes that utilize different ionization and excitation mechanisms found in pulsed glow discharge plasmas.
Cris Lewis, Stephen K. Doorn, David M. Wayne, Fred L. King, and Vahid Majidi, "Characterization of a Pulsed Glow Discharge Laser Ablation System Using Optical Emission," Appl. Spectrosc. 54, 1236-1244 (2000)