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quasi-linear theory negare-ye cunân-xatti Fr.: théorie quasi-linéaire In plasma physics, the theory that considers the interactions between waves and particles are of first order only. It ignores all terms of second order in the fluctuating quantities. |
radio recombination line xatt-e bâzmiyâzeš-e râdioyi Fr.: raie de recombinaison radio 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. |
Rayleigh line xatt-e Rayleigh Fr.: 1) droite de Rayleigh; 2) raie de Rayleigh 1) A straight line that connects the points corresponding to the initial and final states
on a graph of pressure versus specific volume for a substance subjected to a
→ shock wave. The slope of the Rayleigh line is proportional
to the square of shock speed. Steeper Rayleigh lines correspond to higher
shock speeds. See also → Hugoniot curve. |
recombination line xatt-e bâzmiyâzeš Fr.: raie de recombinaison 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. |
rectilinear râst-xatt (#) Fr.: rectiligne In a straight line; consisting of straight lines. → curvilinear From recti- combining form of rectus, → right, + → line + -ar, variant of the adjective-forming suffix → -al. |
rectilinear propagation of light tuceš-e râst-xatt-e nur Fr.: propagation rectiligne de la lumière The motion of light in the first approximation, as evidenced from the formation of shadows and other every day experience. However, → diffraction → rectilinear; → propagation; → light. |
rectilinear system râžmân-e râst-xatt Fr.: système rectilinéaire An optical system that is corrected for → distortion and → spherical aberration and therefore forms the image of a straight line as a straight line. → rectilinear; → system. |
redshifted line xatt-e sorx kibideh Fr.: raie décalée vers le rouge A spectral line whose wavelength does not coincide with its theoretical value and is shifted toward longer wavelengths. |
regression line xatt-e vâyâzeš Fr.: droite de régression The curve representing a → linear regression. It is a line drawn through a set of data that summarizes the relationship between the → variables being studied. → regression, → line. |
resolved line xatt-e vâgošudé Fr.: raie résolue A → spectral line that is not contaminated by other nearby lines. |
resonance line xatt-e bâzâvâyi Fr.: raie de résonance For a particular atom, the spectral line corresponding to the longest wavelength arising from a transition between the ground state and an excited state. |
satellite line xatt-e bandevâr Fr.: raie satellite Radio astro.: Of an OH source, which emits at 1665 and 1667 MHz as the main frequencies, one of the lines arising from transitions at 1612 and 1730 MHz. |
semi-forbidden line 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 (^{3}P_{1}) with a total spin angular momentum S = 1 and the → ground state, a → singlet state (^{1}S_{0}, 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. |
sightline did-xatt Fr.: ligne de visée |
single-lined binary dorin-e tak-xatté Fr.: binaire à une seule raie A → spectroscopic binary in which only one set of → spectral lines is detectable. The binary nature of the system is deduced from the fact that the spectral lines exhibit periodic → Doppler shifts due to orbital motions in the system. Same as → SB1 binary. See also: → double-lined binary. |
snow line marz-e yax, yax-marz Fr.: limite de glace In a → protoplanetary disk, the limit between the regions where water is gaseous and the region where it is cold enough for water to become ice. The core accretion theory predicts that → giant planets form just outside the snow line where they can accrete enough rock and ice to generate a core. Subsequently the core grows into a gas giant like → Jupiter or → Saturn via the → accretion of hydrogen and helium. The snow line location depends on the → luminosity of the central star. For solar system it is about 5 AU, the position of Jupiter. Also known as ice line. |
spectral line xatt-e binâbi Fr.: raie spectrale A dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow wavelength range, compared with the nearby wavelengths. |
spline function karyâ-ye splin Fr.: fonction spline A function consisting of several segments, usually → polynomials, joined smoothly together at specific points with an explicitly stated degree of accuracy. Spline functions are used to approximate a given function on an interval. From East Anglian dialect, maybe related to O.E. splin and to modern splint. A spline was originally a slat or a thin strip of wood. A later meaning was "a long, thin, flexible strip used as a guide for drawing arcs of curves;" → function. |
straight line xatt-e râst (#) Fr.: droite A line without curvature or angles. A line whose → slope is → constant. |
streak line xatt-e xaš Fr.: ligne d'émission In → fluid mechanics, the curve defined by the positions of all particles which have passed through a given point. In laboratory experiments, streak line may be displayed by the stream of color resulting from injection of a dye into the flow. |
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