24 December 1999
Vol 286, Issue 5449

About The Cover

Cover image expansion

COVER An electron colliding with a hydrogen atom to yield two electrons and a proton is the simplest example of electron-impact ionization. Mathematically formulated in the 1950s, this three-body problem in quantum mechanics has required supercomputers for its solution. Shown are wave functions for the breakup of a system of three charged particles. Understanding collisional ionization is essential for problems such as low-temperature plasma formation. See page 2474 [Image: Mark Baertschy and Terry Ligocki]