Re:Precious Gas (Score 1)

You're essentially right -- the guy down the hall (worked with CO2 lasers) says they work through a combination of gases, (nitrogen/hydrogen and CO2). The nitrogen is ionized through some technique -- a glow discharge in this case -- and either the ions or electrons created then excite a particular CO2 state (we don't remember if it is rotational or vibrational.) This takes place in a tuned cavity (a quartz or glass tube of order 1m with mirrors at either end) which selects the wavelength of that particular state's transition eneregy, thus created a surplus of directed energy which excites more and more of the same radiation by resonating with the CO2. Frequency is tunable, to some degree, by changing the cavity length.

He also says efficiency is no concern. I only know that the CO2 laser beam was invisible, and could give you a nasty burn. The cavity for it had a purple (probably nitrogen) glow.

Of course, this topic has probably decayed past the care threshold, given the /. fickle-ity, but the websites for the research groups doing the plasma sheilding work are

http://aprp.stanford.edu/
http://www.ece.odu.edu/~mlarouss/

and it is a real military project.