The Pauli exclusion principle is the quantum mechanical principle that no two identical fermions (particles with half-integer spin) may occupy the same quantum state simultaneously. A more rigorous statement is that the total wave function for two identical fermions is anti-symmetric with respect to exchange of the particles. The principle was formulated by Austrian physicist Wolfgang Pauli in 1925.
For example, no two electrons in a single atom can have the same four quantum numbers; if n, l, and ml are the same, ms must be different such that the electrons have opposite spins, and so on.
Integer spin particles, bosons, are not subject to the Pauli exclusion principle: any number of identical bosons can occupy the same quantum state, as with, for instance, photons produced by a laser and Bose–Einstein condensate.
Read more about Pauli Exclusion Principle: Overview, History, Connection To Quantum State Symmetry
Famous quotes containing the words exclusion and/or principle:
“All men, in the abstract, are just and good; what hinders them, in the particular, is, the momentary predominance of the finite and individual over the general truth. The condition of our incarnation in a private self, seems to be, a perpetual tendency to prefer the private law, to obey the private impulse, to the exclusion of the law of the universal being.”
—Ralph Waldo Emerson (1803–1882)
“... it is not the color of the skin that makes the man or the woman, but the principle formed in the soul. Brilliant wit will shine, come from whence it will; and genius and talent will not hide the brightness of its lustre.”
—Maria Stewart (1803–1879)