An Etymological Dictionary of Astronomy and Astrophysics
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A linear combination of vectors in which all the vector coefficients add up to one.

→ affine; → combination.

1) General: The act of combining or the state of being combined.
2) Math: The number of ways elements making up a set can be arranged into various groups without regard to their order in the group. → permutation

Noun from → combine

A process where a positive molecular ion recombines with an electron, and as a result it dissociates into two neutral products. For example, AB⁺ + e^-→ A + B, where e^- is an electron, AB⁺ is a diatomic or polyatomic molecular ion, and A and B are the neutral fragmentation products. Dissociative recombination is the dominant recombination process in planetary ionospheres and interstellar clouds.

→ dissociative; → recombination.

The process by which an ionized atom binds a free electron in a → plasma to produce a new atomic state with the subsequent radiation of photons.

→ radiative; → recombination.

A → recombination line whose wavelength lies in the radio range of the electromagnetic spectrum. Radio recombination lines are the result of electronic transitions between high energy levels (n > 50) in an atom or ion.

→ radio; → recombination line.

1) The process or result of combining again.
2) The capture of an electron by a positive ion. It is the inverse process to → ionization.

Verbal noun of → recombine.

A measure of the specific rate at which oppositely charged ions join to form neutral particles. It is given by the rate at which those ions recombine, divided by the product of the densities of the two species involved.

→ recombination; → coefficient.

A recombination radiation that is continuous over a range of frequencies. Same as → continuum emission.

→ recombination; → continuum.

Same as → recombination era.

→ recombination; → epoch.

The era some 380,000 years after the → Big Bang (at a → redshift of about 1,100), when the Universe had cooled sufficiently so that protons and electrons combined to form → neutral hydrogen in a process called → recombination. The temperature was about 3,000 K and the ionization fraction low enough for Universe to become transparent to light. Consequently matter and radiation decouple from one another because no further → scattering of the radiation occurs. The observation of the → cosmic microwave background radiation provides a means of studying the Universe at the recombination era. Also called recombination epoch and → decoupling era.

→ recombination; → era.

An → emission line in a spectrum produced in an → H II region when a free electron combines with an ionized atom to form a neutral atom or an ion of lower → ionization stage. Same as → free-bound emission.

→ recombination; → line.

Radiation produced when a free electron in a plasma is captured by an ionized atom.

→ recombination; → radiation.

In → H II regions the rate at which free electrons recombine with → ionized hydrogen atoms (protons).

→ recombination; → rate.

The time period necessary for a cloud of atomic hydrogen to be → ionized by the ultraviolet photons of a central → massive stars.

→ recombination; → time.

An empirical rule discovered before the advent of quantum mechanics which states that it is possible to find pairs of spectral lines, which have the property that the sum of their wavenumbers is also an observed spectral line.

Named after Walther Ritz (1878-1909), a Swiss theoretical physicist; → combination; → principle.