Stern Gerlach experiment

Stern-Gerlach experiment, demonstration of the restricted spatial orientation of atomic and subatomic particles with magnetic polarity, performed in the early 1920s by the German physicists Otto Stern and Walther Gerlach. In the experiment, a beam of neutral silver atoms was directed through a set of aligned slits, then through a nonuniform (non-homogeneous) magnetic field, and onto a cold glass plate. An electrically neutral silver atom is actually an atomic magnet: the spin of an unpaired electron causes the atom to have a North and South Pole like a tiny compass needle. In a uniform magnetic field, the atomic magnet only precesses as the atom moves in the external magnetic field. In a nonuniform magnetic field, the forces on the two poles are not equal, and the silver atom itself is deflected by a slight resultant force, the magnitude and direction of which vary in relation to the orientation of the dipole in the nonuniform field.