The observation of current in the afterglow of the discharge in a pulsed hollow-cathode lamp illuminated by tunable lasers, combined with optogalvanic techniques, provides a simple and reliable tool for multi-step photoionization spectroscopy studies. A three-photon photoionization spectroscopy study was performed in a uranium hollow-cathode lamp, using this combination of techniques. Single-, double-and triple-frequency photoionization paths were identified for uranium, in the range between 5900 and 6060 Å.
In this work a dc discharge with a copper hollow cathode in argon used for deposition applications is investigated using atomic emission spectroscopy. Typical discharge parameters during our investigation are pressures between 80 and 200 P a and current densities up to 7 mA cm −2 . The radial light intensity profiles of some selected copper and argon lines were measured. An analysis of these profiles gives insigths into the excitation rates of the argon filling gas and the sputtered metal atoms as well as into the radial dimension of the negative glow. The different excitation mechanisms lead to a sharp change of the radial light intensity profiles emitted by many copper spectral lines, which indicates the transition region between the cathode fall and the negative glow. The length of the cathode fall was observed to be very insensitive to all the macroscopic discharge parameters. A nearly constant value was found for the cathode fall length, which corresponds to about 22% of the cathode radius.
In this work, we suggest a methodology to determine the impact parameter for neutral dysprosium emission lines from the characterization of the plasma generated by laser ablation in a sealed chamber filled with argon. The procedure is a combination of known consistent spectroscopic methods for plasma temperature determination, electron density, and species concentration. With an electron density of 3.1 × 1018 cm–3 and temperature close to 104 K, we estimated the impact electron parameter for nine spectral lines of the neutral dysprosium atom. The gaps in the impact parameter data in the literature, mainly for heavy elements, stress the importance of the proposed method.
Uranium photoionization was observed in the afterglow of pulsed hollow cathode lamps illuminated by a dye laser tuned near the electronic transition around 591.5 nm ͑ 5 L 6 0 Ϫ16 900 cm Ϫ1 7 M 7 ͒. The photoionization signal was used to monitor the time evolution of the ground state uranium vapor density in the cathode hole. Lifetimes over 1 ms were measured for the uranium vapor; that makes this device attractive for multistep photoionization spectroscopy. The obtained results lead to the conclusion that these long times are due to cluster formation in the afterglow.
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