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

A → philosophy of → mathematics that was introduced by the Dutch mathematician L.E.J. Brouwer (1881-1966). Intuitionism is based on the idea that mathematics is a creation of the mind. The truth of a mathematical statement can only be conceived via a mental construction that proves it to be true, and the communication between mathematicians only serves as a means to create the same mental process in different minds (Stanford Encyclopedia of Philosophy).

→ intuition; → -ism.

The action or of inventing or something invented.

Verbal noun of → invent.

A → scattering process by which fast-moving, energetic particles transfer energy to photons, decreasing the wavelength of the radiation. This is a particularly important effect in astrophysics and cosmology since it explains the → Sunyaev-Zel'dovich effect.

→ inverse; → Compton effect.

Meteo.: A departure from the usual decrease or increase with altitude of the value of an atmospheric property. It almost always refers to a temperature inversion, i.e., an increase in temperature with altitude. Chemistry: To subject to → inversion.

Verbal noun of → invert.

Meteo.: The atmospheric layer in which the temperature gradient is inverted, that is increases; → inversion. The inversion layer tends to prevent the air below it from rising, thus trapping any pollutants that are present.
Electricity: A converting of direct current into alternating current.

→ inversion; → layer.

In atomic physics, a condition in which there are more electrons in an upper energy level than in a lower one, while under normal conditions of thermal equilibrium the reverse is true. → optical pumping.

Inverted, p.p. of → invert; → population.

The act of invoking.

Verbal noun of → invoke.

An atom that has lost or gained one or more electrons and has become electrically charged as the result.

Ion (introduced in 1834 by E. physicist and chemist Michael Faraday), from Gk ion " going," neut. pr.p. of ienai "to go," from PIE base *ei- "to go, to walk," eimi "I go;" cf. Pers. ây-, â- present stem of âmadan "to come;" O.Pers. aitiy "goes;" Av. ay- "to go, to come," aēiti "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go."

Yon, from Fr., from Gk., as above.

The thin glowing streamers in a comet's ion tail.

→ ion; → ray.

Of a comet, same as → gas tail.

→ gas; → tail.

Of or pertaining to ions; occurring in the form of ions.

From → ion + → -ic.

A quantity, pertaining to an ion of a chemical element, expressing the relative number of the ion with respect to that of hydrogen.

→ ionic; → abundance.

A molecule that consists of the ions of the chemical elements that make up the molecule.

→ ionic; → molecule.

The process by which ions are produced, typically occurring by interaction with electromagnetic radiation ("photoionization"), or by collisions with atoms or electrons ("collisional ionization").

Verbal noun of → ionize.

A quantity used in studies of → emission nebulae to convert the → ionic abundance of a given chemical element to its total → elemental abundance. The elemental abundance of an element relative to hydrogen is given by the sum of abundances of all its ions. In practice, not all the ionization stages are observed. One must therefore correct for unobserved stages using ICFs. A common way to do this was to rely on → ionization potential considerations. However, → photoionization models show that such simple relations do not necessarily hold. Hence, ICFs based on grids of photoionization models are more reliable. Nevertheless here also care should be taken for several reasons: the atomic physics is not well known yet, the ionization structure of a nebula depends on the spectral energy distribution of the stellar radiation field, which differs from one model to another, and the density structure of real nebulae is more complicated than that of idealized models (see, e.g., Stasińska, 2002, astro-ph/0207500, and references therein).

→ ionization; → correction; → factor.

Same as → ionization potential.

→ ionization; → energy.

An abrupt discontinuity between an H II region and the molecular cloud in which it has formed. In this transition region interstellar gas changes from a mostly neutral state to a mostly ionized state.

→ ionization; → front.

A ratio representing the number of ionizing photons to the number of electrons in a nebular emitting region.

→ ionization; → parameter.

The energy required to remove an electron from an isolated atom or molecule. The ionization potential for hydrogen is 13.6 eV, which corresponds to an ultraviolet ionizing photon with a wavelength of 912 A. Also called → ionization energy.

→ ionization; → potential.

The spatial distribution of ionic species around an ionization source according to their → ionization potentials. The higher the ionization potential, the nearer to the source the corresponding ions will be.

→ ionization; → stratification.