An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) To give and receive reciprocally.
2) The act, process, or an instance of exchanging. → exchange force, → exchange particle, → Prevost's law of exchanges.

O.Fr. eschangier, from V.L. *excambiare, from L. → ex- "out" + cambire "barter."

Mod.Pers. gahulidan "to exchange," Kurd. guhartin/guhêr- "to exchange," Mid.Pers. wihir "to change," wihirišn "change," Manichean Mid.Pers. hr'g; Buddhist Mid.Pers. hlg "duty, tribute; work, effort;" Arm. loanword hark "duty, tribute;" Ar. loanword xarj "expense," xarâj "land, property tax;" Proto-Iranian *har- "to barter, trade; to pay tribute;" IE cognates: Gk. elein "to take (by force)," elor "loot, booty, catch;" Goth. saljan "to bring, to sacrifice;" O.E. sellan "to hand over, sell;" O.H.G. sala "delivery of goods."

The force that governs the exchange of particles in the interaction between bodies. → exchange particle.

→ exchange, → force.

In quantum field theory, a particle that transfers momentum and energy between interacting objects, and is said to mediate the interaction. All four of the fundamental forces involve the exchange of one or more particles. For example, photon is the exchange particle of the electromagnetic force.

→ exchange, → particle.

Chemistry: A complex formed from combination of a molecule with another molecule of the same type but in an → excited state. In other words, a → dimer in an electronically excited state. See also → exciplex.

From exci-, from → excited, + -mer, from → dimer.

Chemistry: A complex formed by association of a molecule in an → excited state and another molecule of a different type. See also → excimer.

From exci-, from → excited, + -plex, from → complex.

For a → triangle with two sides extended in the direction opposite their common → vertex, a circle that lies outside the triangle and is tangent to the three sides (two of them extended). The center of the excircle, called the → excenter, is the point of intersection of the bisector of the interior angle and the bisector of the exterior angles at the other two vertices.

→ ex-; → circle.

To cut out or off; to remove

M.E., from M.Fr. exciser, from L. excisus, p.p. of excidere "cut out, cut down, cut off," from → ex- + caedere "to cut," → precise.

Osunidan, from os-, → ex- + sun "cut," → precise.

The act of removal; an excising. The surgical removal of a foreign body or of tissue.

Verbal noun of → excise.

1) The addition of → energy to an → atomic or → molecular system, → transferring it from its → ground state to an → excited state.
2) A property of an → emission nebula usually expressed by the ratio [O III] 5007Å/Hβ.

Verbal noun of → excite; → -tion.

Amount of energy (usually measured in → electron-volts) required to bring an electron from its → ground state to a given → excited state.

→ excitation; → energy.

In quantum mechanics, the energy that is necessary to change a system from a → ground state to a given → excited state; also called excitation energy.

→ excitation; → potential.

Of a gas or plasma, the temperature deduced from the → populations of atomic → excited states, as expressed by the Boltzmann formula: N_u/N_l = (g_u/g_l) exp (-ΔE/kT_ex), where N_u and N_l are the upper level and lower level populations respectively, g_u and g_l the statistical weights, ΔE = hν the energy difference between the states, k is → Boltzmann's constant, and h→ Planck's constant. The higher the energy of the occupied states, the higher the excitation temperature.

→ excitation; → temperature.

Verb of → excitation.

From L. excitare "to rouse, produce," freq. of exciere "to call forth, instigate," from → ex- "out" + ciere "to move, set in motion;" PIE base *kei- "to move to and fro" (cf. Av. šiyav-, š(ii)auu- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" Mod.Pers. šodan, šow- "to go; to become;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. seuo "I start quickly after," kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call").

Barangixtan, from intensive prefix bar- "on, upon, up," → on-, + angixtan, angizidan "to excite, stimulate," from Mid.Pers. hangêxtan, hangêz- "to arouse, stimulate, stir up," from Proto-Iranian *hamgaiz-, from ham-, → com-, + *gaiz- "to disturb, stir, excite." The Mod.Pers. gij, giž "confused, astonished, dizzy" is from this stem (Cheung 2007).

An atom in which one or more of its bound electrons are at → energy levels higher than their normal level.

Excited p.p. of → excite; → atom.

The condition of a particle or system of particles (especially an atom, nucleus, molecule) after absorbing energy from outside and transiting to a higher → energy level than that of its → ground state. Excited states are transitory as they lose energy through emissions or collisions and return to ground state.

Excited, p.p. of → excite; → state.

A star associated with an interstellar ionized nebula (→ H II region or → planetary nebula) whose energetic → ultraviolet, → photons → ionize the nebula.

Exciting, verbal adj. of → excite; → star.

To shut or keep out; to hinder from being included, considered, or accepted. → exclusion.

From L. excludere "to keep out, shut out, hinder," from → ex- "out" + claudere "to close, shut," → include.

Sokolândan, from so-, variant os-, → ex-, + kolândan "to shut," → include.

An act or instance of excluding; the state of being excluded.

Verbal noun of → exclude.

In → quantum mechanics, the principle according to which no → two → fermions of the same kind may simultaneously → occupy the same → quantum state. Also known as → Pauli exclusion principle.

→ exclusion; → principle.

Excluding or having power to exclude; excluding all else; rejecting other considerations, possibilities, etc.

Adj. from → exclude.