There was some more recent work done on breaking down air with a high power
photon pulse (Q-switched YAG laser focussed to a small spot).  You might
check there.  Dan Neal published a paper recently at SPIE I think.

Justin D. Mansell                | "If your opponent strikes with fire,
Ginzton Laboratory               |         counter with water."
Stanford, CA 94305               | "To injure an opponent is to injure
tel: 650-725-2266                |          yourself."
fax: 650-723-2666                |              -Morihei Ueshiba
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