In the previous blog, I talked about incandescence and how heating a material is utilized to produce light, inefficiently. The broad range of electromagnetic radiation emitted from the source is due to a plethora of different interactions on the atomic level each resulting in a specific amount of energy release.
A very simplified list of interactions => energy is as follows:
Molecular rotation => microwave energy
Molecular vibration => infrared energy (~heat)
Electron orbital shifts => visible energy (~light)
If someone wants to improve lighting efficiency, one has to focus on maximizing electron orbital shifts. And this is where plasma come in.
If you are not familiar with plasma, don’t feel too bad. A plasma occurs when there is enough energy present to strip the electrons from their atoms. This results in this hot, disorderly mess of atom nuclei and run-away electrons. The most naturally occurring forms of plasma in our lives are the sun in the sky and lightning in thunderstorms.
Turns out that since stars are what make up almost all that we see in space, plasma makes up >99% of our visible universe. And as long as I’m the minority [AKA, not a plasma], that’s cool!
To create a gas-discharged plasma, follow these steps!
1) Contain a gas in a glass tube (preferably at low pressure)
2) Stick electrodes at the ends [which don’t melt]
3) Find a high voltage power source and attach to the electrodes
4) Throw back the massive ON switch and laugh menacingly! [Maybe wear UV glasses too, with the cool, dark tint]
The unique thing about plasma is that since the electrons are stripped away, there is no longer any atomic bonds available for molecular rotations and vibrations. Keeping the gas pressure low further reduces the amount of energy released from atom-atom interactions.
Thus, the main form of energy release is in the form of electrons shifting orbitals in the atoms. If you have taken quantum physics, you also know that these orbitals are “quantized.” And based on these specific orbital levels, the atom can only give off specific colors of light [its Atomic Emission Spectrum].
Hydrogen: Red, Cyan, and Purples
Helium: Dark Red, Yellow, Aquamarine, Blues, and Purples
Thus, each atom on the periodic table has its own unique atomic “finger print.” It’s one way we can determine how much Helium/Carbon/Iron/Etc. exists in a star. Or a burning flame. That is also why we can get packets of “magical dust” that turn your campfire green!
By mixing and matching gases [Noble Gas / Mercury Vapor / Metal Halide / Sodium Vapor], one can create varying levels of color, white warmth, and intensity! Also, any metals can also easily vaporize into a gas form, expanding your possibilities (Yay, gaseous Mercury!).
And since you can’t “melt” a gas, you can pump out A LOT of visible energy to illuminate a large area from a single unit. This makes them great for large audience venues (stadiums), movie theater projectors, and car headlamps.