Influences of voltage shape and discharge gas on the temporally and spatially resolved emission characteristics of tin in a planar dielectric barrier discharge

Highlights: • Emission characteristics of Sn in a DBD was made visible with temporal resolution of 5 ns • Square wave generator delivers power in one single discharge event • With sinusoidal generator the discharge ignites multiple times over a long time period • Change of discharge gas is more severe for the Sn signal in a sinusoidal excited plasma than in square wave excited plasma -- Abstract: Choosing a suitable power supply concerning the shape of the excitation voltage and the type of discharge gas for elemental analysis with a dielectric barrier discharge is not trivial. Both significantly affect the analyte signal. By means of conventional methods such as inductively coupled plasma mass spectrometry or atomic absorption spectrometry optimal conditions can be found, however the reason why the specific parameter set results in ideal signals is hidden in the detailed characteristics of the DBD. These phenomena occur on a narrow time scale of nanoseconds to microseconds and are challenging to observe. Therefore, the emission profiles of tin in a planar dielectric barrier discharge atomizer were studied by means of temporally and spatially resolved optical emission spectroscopy by varying the type of discharge gas and the shape of the excitation voltage. The latter was realized by applying either a sinusoidal or a square wave power supply. The temporally resolved emission profile showed that in case of sinusoidal excitation the power is distributed over a longer time in several discharge events, whereas with square wave excitation the power is coupled to the dielectric barrier discharge in one intensive pulse. The spatially resolved emission signals indicated a different point of excitation of Sn within the dielectric barrier discharge for each power source. The Sn emission in a plasma, which was sustained by the square wave power supply, was not significantly influenced by the change of the discharge gas from argon to helium. However, for the emission signal in a plasma excited by the sinusoidal power supply, helium had an adverse effect.