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.
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.
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.
In a straight line; consisting of straight lines. → curvilinear
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
Fr.: système rectilinéaire
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.
Fr.: droite de régression
Fr.: raie résolue
A → spectral line that is not contaminated by other nearby lines.
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.
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.
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.
Fr.: ligne de visée
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.
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.
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.
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.
xatt-e râst (#)
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.