photon-atom dipole interaction
21Muon — The Moon s cosmic ray shadow, as seen in secondary muons generated by cosmic rays in the atmosphere, and detected 700 meters below ground, at the Soudan II detector Composition Elementary particle Statistics …
22Nonlinear optics — (NLO) is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the dielectric polarization P responds nonlinearly to the electric field E of the light. This nonlinearity is typically only observed… …
23Stimulated emission — In optics, stimulated emission is the process by which an electron, perturbed by a photon having the correct energy, may drop to a lower energy level resulting in the creation of another photon. The perturbing photon is seemingly unchanged in the …
24Magnetometer — A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature. Some countries such as the USA, Canada and Australia classify the more sensitive… …
25Precision tests of QED — Quantum electrodynamics (QED), a relativistic quantum field theory of electrodynamics, is among the most stringently tested theories in physics.Precision tests of QED consist of measurements of the electromagnetic fine structure constant, α, in… …
26cosmos — /koz meuhs, mohs/, n., pl. cosmos, cosmoses for 2, 4. 1. the world or universe regarded as an orderly, harmonious system. 2. a complete, orderly, harmonious system. 3. order; harmony. 4. any composite plant of the genus Cosmos, of tropical… …
27Spontaneous emission — is the process by which a light source such as an atom, molecule, nanocrystal or nucleus in an excited state undergoes a transition to the ground state and emits a photon. Spontaneous emission of light or luminescence is a fundamental process… …
28ionosphere and magnetosphere — ▪ atmospheric science Introduction regions of Earth s (Earth) atmosphere in which the number of electrically charged particles ions (ion) and electrons (electron) are large enough to affect the propagation of radio waves (electromagnetic… …
29Mössbauer effect — Physics. the phenomenon in which an atom in a crystal undergoes no recoil when emitting a gamma ray, giving all the emitted energy to the gamma ray, resulting in a sharply defined wavelength. [1955 60; named after R. MÖSSBAUER] * * * ▪ physics… …
30Atomic nucleus — A figurative depiction of the helium 4 atom with the electron cloud in shades of gray. In the nucleus, the two protons and two neutrons are depicted in red and blue. This depiction shows the particles as separate, whereas in an actual helium atom …
