Fr.: transition atomique
A change in the → energy level or → state of an → atom in which a → quantum of energy is either gained or lost. See also → forbidden transition; → permitted transition; → semiforbidden transition.
→ atomic; → transition.
Fr.: transition liée-liée
A transition between two energy levels of an electron bound to a nucleus. The electron remains tied to the nucleus before and after the transition. → bound-free transition; → free-free emission.
Bound, p.p. of → bind; → transition.
Fr.: transition liée-libre
A transition in which a bound electron is liberated. → free-bound emission; → free-free emission.
Fr.: transition en cascade
A photon generation mechanism in an atom in which a transition initiates a series of secondary transitions from lower electronic levels.
→ cascade; → transition.
Fr.: transition discrète
A transition between two quantum-mechanical energy levels. See also → discrete spectrum.
→ discrete; → transition.
Fr.: transition électronique
The → transfer of an → electron from one → energy level to another.
→ electronic; → transition.
Fr.: transition interdite
A transition between two quantum mechanical → states that → violates the quantum mechanical → selection rules.
→ forbidden; → transition.
Fr.: transition hyperfine
An → atomic transition involving a → hyperfine structure.
→ hyperfine; → transition.
A change in the → energy level or state of an atomic → nucleus involving a → quantum of energy.
→ nuclear; → transition.
Fr.: transition permise
A transition between two quantum mechanical states that does not violate the quantum mechanical selection rules.
→ permitted; → transition.
Fr.: transition de phase
The changing of a substance from one phase to another, by → freezing, → melting, → boiling, → condensation, or → sublimation. Also known as phase transformation. A well known phase transition is the transition from → water to → ice. Phase transitions are often associated with → symmetry breaking. In water there is a complete symmetry under rotations with no preferred direction. Ice has a crystal structure, in which certain orientations in space are preferred. Therefore, in transition from water to ice the continuous rotational symmetry is lost.
→ phase; → transition.
quantum phase transition (QPT)
gozareš-e fâz-e kuântomi
Fr.: transition de phase quantique
A phase transitions that occurs at zero temperature as a function of a non-thermal parameter like → pressure, → magnetic field, or → chemical composition. In contrast to ordinary → phase transitions, which are associated with passage through a critical temperature, quantum phase transitions are associated with → quantum fluctuations, a consequence of → Heisenberg's uncertainty principle. For example, see → Bose-Einstein condensation.
→ quantum; → phase; → transition.
quark-hadron phase transition
gozareš-e fâz-e kuârk-hâdron
Fr.: transition de phase quark-hadron
A phase transition, predicted by cosmological models, to have occurred at approximately 10-5 seconds after the Big Bang to convert a plasma of free quarks and gluons into hadron.
→ quark; → hadron; → phase; → transition.
Fr.: transition radiative
A transition between two states of an atomic or molecular entity, the energy difference being emitted or absorbed as photons.
→ radiative; → transition.
Fr.: transition rotationnelle
A slight change in the energy level of a molecule due to the rotation of its constituent atoms about their center of mass.
→ rotational; → transition.
Fr.: transition semi-interdite
An → atomic transition whose probability is reduced by a factor of the order of 106 because of → selection rules. Same as → interconnection line.
→ semi-; → forbidden; → transition.
Fr.: transition spontanée
An → atomic transition that gives rise to a → spontaneous emission.
→ spontaneous; → transition.
1) Passage from one position, state, stage, subject, concept, etc., to another.
From L. transitionem (nominative transition) "a going across or over," noun of action from transire "go or cross over," from → trans- "across" + ire "to go."
Gozareš, verbal noun of gozaštan "to transit, pass," → transit, + -eš, → -tion.
gerde-ye gozaresh, disk-e ~
Fr.: disque de transition
The → accretion disk of a → T Tauri star that displays very weak or no → infrared excess at → near infrared wavelengths, but shows strong excess at → intermediate infrared and longer wavelengths. This happens when the hot inner dust disk has dissipated whereas the cooler outer disk is still intact.
→ transition; → disk.
Fr.: fonction de transition
The → probability of finding the → Universe in a → state labelled X2 at a time t2, if it was in a state X1 at an earlier time t1.
→ transition; → function.