Europium (Eu) in plasma

Europium burns a hard white ring inside a flask flooded with violet and blue, and at lower drive it shifts towards magenta. It is the lanthanide behind the red phosphors in old television screens, and the same transitions that made those tubes glow are at work here, just with a discharge instead of an electron beam doing the exciting.

Europium fluoride. Blue tint comes from XeF excimer

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• Europium (Eu) glowing plasma discharge, video 18 of 18

Periodic Table of Plasma