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: 4 Search : semi-
semi-
  نیم-، نیمه-   
nim- (#), nimé- (#)

Fr.: semi-, demi-   

A combining form meaning "half," freely prefixed to English words of any origin.

From L. semi- "half," from PIE *semi-; cf. Skt. sāmi "half," sāmi-krita- "half-done;" Gk. hemi- "half;" O.E. sam-; Goth. sami- "half."

Nim, nimé "half," from Mid.Pers. nêm, nêmag "half;" Av. naēma- "half;" cf. Skt. néma- "half."

semi-forbidden line
  خط ِ نیمه-بژکم   
xatt-e nime-bažkam

Fr.: raie semi-interdite   

A → spectral line for which the upper and lower → energy levels have different values of S, the total → spin angular momentum. These lines violate the quantum mechanical → selection rule under → LS coupling, ΔS = 0. For example, the Ca I λ6573 line results from transition between the upper → triplet state (3P1) with a total spin angular momentum S = 1 and the → ground state, a → singlet state (1S0, total spin angular momentum S = 0). A semi-forbidden line is marked by a right bracket following the atom name, i.e. Ca I], in the above-mentioned case. Same as → interconnection line and → intersystem line.

semi-; → forbidden; → line.

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.

semi-major axis
  آسه‌ی ِ نیمه‌مهین   
âse-ye nimeh-mehin

Fr.: demi grand axe   

Half the length of the major axis of an ellipse; a standard element used to describe an elliptical orbit. see orbital elements

semi-; → major; → axis.