delta ionization: Stratified symmetrical electron emission and resonantly structured ionization continuum

We have discovered theoretically that ionization of a one-dimensional quant um well by an ultrashort subcycle (delta-like) electromagnetic pulse result s in photoelectrons propagating both along the field and in the opposite di rection in well-separated shells whose velocities reflect quasiresonances i n the ionization continuum. For both a quantum well and a three-dimensional hydrogenlike atom, a unipolar, i.e., strongly asymmetrical, delta ionizati on produces an approximately symmetrical, stratified photoelectron cloud. [ S1050-2947(99)09701-2].