A sharp burst of laser light striking an atom can yank away an electron, ionizing the atom. If the laser pulse is extremely intense, the rapid oscillations of its electric field pull off multiple electrons, one after another. In the mid-1980s, however, amazed researchers discovered that moderately intense laser beams dislodge multiple electrons at a rate up to a million times higher than expected and, seemingly, in groups of two or more. Since then, researchers have furiously debated explanations for those findings.
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