Parametric studies of emission from a plasma gun source for atomic spectroscopy

Abstract

A detailed parametric study of the effects of electrical discharge parameters on the spatially and temporally resolved emission from the expelled plume of a plasma gun atomic emission source was performed. Expulsion properties were found to depend on the d I/d t of the discharge current. Low-inductance discharges produced plasmas with propagation velocities (about 1.2 km s −1) which were independent of discharge energy and probably controlled by the properties of the support gas in the discharge chamber. Added-inductance discharges produced plumes with significantly lower propagation velocities and less efficient atomization and expulsion of analyte. Continuum background emission was attributable to two processes, depending upon the spatial location in the plasma: decaying background from the rapidly cooling expelled plasma (lower regions) and collision of the initially-expelled plasma with some of the continuously-expelled plasma gun vapor (upper regions). The line-to-background ratio is optimized when using the highest-energy, low-inductance discharges coupled with integration of emission only from the upper regions of the plume (>10 mm) after the first emission pulse (> 75 μs).