By surfing the net I learned that lasers can be used to ionize air and even produce "bangs" for some reason. Now, what I'm after is to ionize hydrogen or deuterium gas, at either 1 atm pressure or reduced pressure, say 40 mbar. Now what kind of laser light would be best to use? A hideously strong green laser perhaps? Or a strong 405 nm laser? Which is cheapest per watt laser light? UV lasers are probably too expensive. What about using a strong UV-lamp? There are apparently two ways for ionization; either multiphoton or some sort of resonance of the electrons in the changing electric field of the laser light; now which applies to ionization of hydrogen or deuterium? All input welcome!