toc1955's video: Creating Color F-centers with a Tesla Coil

(Adolf Cortel, December 2021). Long ago I was amazed by reading how the discharge of a Tesla coil could induce the creation of F-centers in alkaline halides (Ellis A.B. et al (1993)“Teaching General Chemistry. A Materials Science Companion” American Chemical Society). Recently I came across some nice videos showing how this is easily achieved: https://chem.beloit.edu/edetc/cineplex/Fcenter/index.html From the description given in these sources it seemed that a high vacuum was necessary, but when trying the experiment I checked that a pump used for air conditioning service (limit at 20 mTorr) works well and the color develops very quickly. For convenience of use, I have used as a Tesla coil a vintage high frequency electro-medical apparatus. It has a wand which is placed under the tube containing the samples (and connected to the vacuum pump). I let the pump working for around 15 minutes and when the high frequency current is switched on the color begins developing. One or two minutes are enough, longer expositions produce a heating that can bleach the sample. I suppose that other conventional Tesla coils must work also well. The samples I had available to produce F-centers are : halite (from the mines of Cardona, Barcelona) which becomes yellow; sylvite (from the mines of Suria, Barcelona) which turns violet. I have tried also potassium iodide (synthetic chemical) and Maldon salt. I have not been successful with coloring fluorite which was actually the aim when tried the experiment. It can be checked that the F-centers are removed and the samples become bleached slowly with time, particularly potassium iodide. UV radiation from SW or LW lamps, as well as heating bleach the samples quickly. At the dark it can be seen that “irradiated” Maldon salt placed on a hot plate is thermoluminescent (this is better seen with bare eyes than captured with a camera).