Tuesday, June 21, 2016

The Elements Nobody Talks About: Xenon

The inert gasses (helium, neon, argon, krypton, xenon, radon) are the elements you never hear much about. Sure, we worry about radon gas, and helium gets a good workout in balloons, but when was the last time somebody mentioned krypton at a cocktail party? (Come to think of it, when was the last time you actually attended a cocktail party?) The inert gasses are the lazy elements -- they just lie around all day in the hammock and never do anything. If I were an element, I would want to be be an inert gas.

And that applies especially to xenon. Until recently, if you'd asked me about the main uses of xenon, I would have said it was useful primarily in Scrabble. But within the last couple of years, xenon has become one of the most important elements in cosmology.

Why? For several decades, physicists have been building detectors to search for dark matter, which makes up about 80% of the matter in the universe, far outnumbering the ordinary matter that we're made of. They've built huge containers of "stuff" far underground (abandoned mines are a favorite site) and they've been waiting for the dark matter to strike an atomic nucleus inside this "stuff" so that they can detect the recoil.

And -- you guessed it --- one of the favorite materials to use as a target is xenon. It's not xenon gas, but liquefied xenon -- enormous quantities of it in experiments such as XENON1T (which actually uses, not one ton, but three tons of liquid xenon!) and LUX. So far, these experiments have seen no dark matter, but if they finally do see something, the element xenon will finally get its place in history.


robinpraytor said...

Fascinating stuff! (Krypton is mentioned often in conversations at ou house. No, wait ... it's kryptonite.)

Kathy said...

Neon is used in some fluorescent lights, or was. Hence "neon lights," and why you can't go to Vegas and not hear or see the word "neon" a few times (ie Neonopolis, The Neon museum, etc.)

I've no idea what uses there are for argon and krypton. But wouldn't heavier-than-air inert gases make for good fire extinguishers?