Abstract
This paper describes a new excitation source for emission spectrometry consisting of an r.f. helium glow-discharge plasma and a laser-diode pumped Q-switched Nd : YAG laser. The Nd : YAG laser works dominantly as a sampling source for introducing of sample atoms into the helium glow-discharge plasma, because the laser-induced plasma, which may excite the sample atoms, cannot be produced by the laser itself due to its high repetition rate. On the other hand, the helium glow-discharge plasma mainly acts as an excitation source, because small amounts of the sample atoms can be introduced due to the low sputtering rate. However, the excited species of helium has the excitation capability for sample atoms requiring large excitation energies due to the high metastable levels. From these characteristics in this combined emission source, the sampling process and the excitation process could be controlled independently. Furthermore, it was possible to excite analyte elements having high excitation energies. In this paper, fluorine atomic lines requiring an excitation energy of about 14 eV were measured. These lines were detected only when the laser was irradiated to the helium plasma. The calibration curve for the FI 685.60-nm line gave a linear relationship in a LiF concentration range of 0.02∼5.0 mass%.
