An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 21 Search : transition
atomic transition
  گذرش ِ اتمی   
gozareš-e atomi

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.

bound-bound transition
  گذرش ِ بندیده-بندیده   
gozareš-e bandidé-bandidé

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.

bound-free transition
  گذرش ِ بندیده-آزاد   
gozareš-e bandidé-âzâd

Fr.: transition liée-libre   

A transition in which a bound electron is liberated. → free-bound emission; → free-free emission.

Bound, p.p. of → bind; → free.

cascade transition
  گذرش ِ پی‌شاری   
gozareš-e peyšâri

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.

discrete transition
  گذرش ِ گسسته   
gozareš-e gosasté

Fr.: transition discrète   

A transition between two quantum-mechanical energy levels. See also → discrete spectrum.

discrete; → transition.

forbidden transition
  گذرش ِ بژکم   
gozareš-e bažkam

Fr.: transition interdite   

A transition between two quantum mechanical → states that → violates the quantum mechanical → selection rules.

forbidden; → transition.

hyperfine transition
  گذرش ِ اَبَرنازک   
gozareš-e abar-nâzok

Fr.: transition hyperfine   

An → atomic transition involving a → hyperfine structure.

hyperfine; → transition.

nuclear transition
  گذرش ِ هسته‌ای   
gozareš-e haste-yi

Fr.: transition   

A change in the → energy level or state of an atomic → nucleus involving a → quantum of energy.

nuclear; → transition.

permitted transition
  گذرش ِ پرزامیده   
gozareš-e parzâmidé

Fr.: transition permise   

A transition between two quantum mechanical states that does not violate the quantum mechanical selection rules.

permitted; → transition.

phase transition
  گذرش ِ فاز   
gozareš-e fâz

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)
  گذرش ِ فاز ِ کو‌آنتومی   
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
  گذرش ِ فاز ِ کو‌آرک-هادرون   
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.

radiative transition
  گذرش ِ تابشی   
gozareš-e tâbeši

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.

rotational transition
  گذرش ِ چرخشی   
gozareš-e carxeši

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.

semi-forbidden transition
  گذرش ِ نیمه-بژکم   
gozareš-e nime-bažkam

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.

transition
  گذرش   
gozareš

Fr.: transition   

1) Passage from one position, state, stage, subject, concept, etc., to another.
2) A change between phases such as solid to liquid or liquid to gas.
3) A change in the → energy level or state of an atom or nucleus. → atomic transition, → bound-bound transition, → bound-free transition, → cascade transition, → discrete transition, → forbidden transition, → hyperfine transition, → nuclear transition, → permitted transition, → phase transition, → quark-hadron phase transition, → radiative transition, → rotational transition, → semi-forbidden transition, → transition disk, → transition function, → transition probability, → vibrational transition.

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.

transition disk
  گرده‌ی ِ گذرش، دیسک ِ ~   
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.

transition function
  کریای ِ گذرش   
karyâ-ye gozareš

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.

transition probability
  شوانایی ِ گذرشی   
šavânâyi-ye gozareši

Fr.: probabilité de transition   

The probability that a quantum-mechanical system will make a transition from a given initial state to a given final state.

transition; → probability.

transitional flow
  تچان ِ گذرشی   
tacan-e gozareši

Fr.: flux de transition   

In fluid mechanics, a flow composed of → laminar and → turbulent flows, for which the → Reynolds number is between 2300 and 4000.

transition; → flow.

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