Atomic recoil Atomic recoil Atomic recoil is the result of the interaction of an atom with an energetic elementary particle, when the momentum of the interacting particle is transferred to the atom as whole without altering non-translational degrees of freedom of the atom. It is a purely quantum phenomenon. Atomic recoil was discovered by Harriet Brooks, Canada's first female nuclear physicist. If the transferred momentum of atomic recoil is enough to disrupt the crystal lattice of the material, a vacancy defect is formed; otherwise a phonon is generated. Closely related to atomic recoil is electron recoil (see photoexcitation and photoionization), and nuclear
Charge (physics) a particular representation of that symmetry; the charge quantum number is then the weight of the representation. Various charge quantum numbers have been introduced by theories of particle physics. These include the charges of the Standard Model: Charges of approximate symmetries: Hypothetical charges of extensions to the Standard Model: In supersymmetry: In conformal field theory: In gravitation: In the formalism of particle theories, charge-like quantum numbers can sometimes be inverted by means of a charge conjugation operator called C. Charge conjugation simply means that a given symmetry group occurs in two inequivalent (but still isomorphic) group representations. It is usually