Fr.: désintégration Alpha
The radioactive transformation of a nuclide by alpha-particle emission. Also called alpha disintegration.
tabâhi-ye betâ (#)
Fr.: désintegration bêta
The transformation of a → radioactive nuclide in which a → beta particle is emitted. In beta minus decay, a → neutron changes into a → proton, → antineutrino, and → electron: n → p + e + ν-. Beta plus decay involves the conversion of a proton to a neutron, → positron, and → neutrino: p → n + e+ + ν.
Beta (β), from → beta particle; → decay.
beta minus decay
tabâhi-ye betâ kaman
Fr.: désintegration bêta moins
→ beta particle; → minus; → decay.
beta plus decay
tabâhi-ye betâ bišan
Fr.: désintegration bêta plus
→ beta particle; → plus; → decay.
Fr.: désexcitation collisionnelle
The process when the energy difference between the excited and non excited states of an atom is taken away by an electron during a collision.
→ collisional; → decay.
dark matter decay
tabâhi-ye mâde-ye târik
Fr.: désintégration de la matière noire
In theoretical models, the hypothetical transformation of a → non-baryonic dark matter particle when symmetry is violated at special physical conditions. Dark matter decay and → dark matter annihilation are expected to produce enormous amounts of energy in the form of gamma-rays, cosmic rays, etc.
1) tabâhidan (#); 2) tabâhi (#), forupâši (#)
Fr.: 1) se désintegrer, se désexciter; 2) désintegration, désexcitation
1a) To become decomposed.
From O.Fr. decair, from V.L. *decadere "to fall off," from L. cadere "to fall," PIE base *kad- "to fall" (cf. Pers. Gilaki katan "to fall," ba.ka.tam "I fell," dakatan "to fall (in a marsh, in a pit)," vakatan "to fall from tiredness, be exhausted," fakatan "to fall from (lose) reputation," Pers. Laki: katen "to fall," kat "he fell," beko "fall!," Pers. Tabari: dakətə "fallen," dakətən "to crash down," dakət.gu "stray cow," Arm. chacnum "to fall").
Tabâhidan, verbal form of tabâhi, noun form of tabâh "spoiled, ruined, destroyed," Mid.Pers. tapâh "spoiled, destroyed." Maybe related to Mod.Pers. tâb "affliction, pain, torment; heat, burning," tab "fever," tâbidan, tâftan "to shine," tafsidan "to become hot," Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth," cf. Skt. tap- "to spoil, injure, damage; to suffer; to heat, be/become hot," tapati "burns," L. tepere "to be warm," tepidus "warm," PIE base *tep- "warm."
Fr.: chaîne de désintégration
A series of nuclear decays produced by successive → daughter products, when the daughters are themselves → radioactive. For example, the decay chain N1→ N2→ N3→ ... in which the parent nuclide N1 decays to the daughter N2, which in turn decays to N3. Each → radionuclide in the decay chain can → branch to more than one daughter.
Fr.: constante de désintégration
A constant of proportionality occurring in the formula expressing spontaneous → decay of → radionuclides. The number of atoms decaying is given by N = N0e-kt, where N0 is the number of nuclei in the given volume of the substance at instant t = 0, N is the number of nuclei at t, and k is decay constant. Decay constant is related to → half-life by τ = ln2/k, roughly 0.693/k.
tarz-e tabâhi, mod-e ~
Fr.: mode de désintégration
A possible type of decay of a → radionuclide or → elementary particle. In general, a given particle may decay by more than one decay mode. Usually the number of decay modes is one or two. There are, however, → nuclides which have many decay modes; for example the nuclide 11Li has seven decay modes.
Fr.: produit de désintégration
A → stable nuclide or → radioactive nuclide formed by the → disintegration of a → radioactive isotope, either directly or as a result of a → decay chain. Also called → daughter product. For example, the decay product of 238U is 206Pb, after passing through the following chain: 238U → 234Th (4.5 billion yr) → 234Pa (24 days) → 234U (1 min) → 230Th (245,000 yr) → 226Ra (76,000 yr) → 222Rn (1,600 yr) → 218Po (3.8 d) → 214Pb (3 m) → 214Bi (27 m) → 214Po (160 microseconds) → 210Pb (22 yr) → 210Bi (5 d) → 210Po (138 d) → 206Pb.
zamân-e tabâhi (#)
Fr.: temps d'amortissement
The time required for the amplitude of a vibrating system to decrease
to 1/e of its initial value.
tabâhi-ye gâmâ (#)
Fr.: désintégration gamma
A type of → radioactivity in which some unstable atomic nuclei dissipate excess energy by a spontaneous electromagnetic process, usually accompanied by → alpha decay or → beta decay.
inverse beta decay
tabâhi-ye vârun-e β (#)
Fr.: désintégration β inverse
A collision of a proton with an electron that produces a neutron and an electron neutrino. See → beta decay.
Ohmic decay time
zamân-e tabâhi-ye Ohmi
Fr.: temps de dissipation ohmique
An upper bound on the time scale on which the magnetic field of a system would decay in the absence of any other agent. It is expressed as: τμ = R2 / μ, where R is the scale size of the system, η the magnetic diffusivity (η = 1 / μσ, where μ is the magnetic permeability and σ the electrical conductivity). For a star like the Sun, τμ ≅ 1010 years, so a fossil magnetic field could survive for the star's lifetime on the main sequence. For the Earth, τμ ≅ 104 years, so a → dynamo is required to explain the persistence of the geomagnetic field.
Fr.: déclin d'orbite
A gradual change in the orbit of a spacecraft caused by aerodynamic drag of a planet's outer atmosphere and other forces.
A phase in the → light curve evolution of eruptive objects such as → dwarf novae, → Soft X-ray Transients, and transient → magnetars which follows the characterized sudden increase in their flux (over a factor ~ 1000 over the quiescent level). Outburst decay is slow and lasts months or years.
Fr.: désexcitation radiative
The process when the energy difference between the excited and non excited states of an atom is taken away by radiation.
Fr.: désintégration radioactive
Spontaneous emission by a nucleus of photons or particles.
→ radioactive; → decay.
Fr.: dissipation de turbulence
The process whereby turbulence evolves by exchanging energy, leading to → dissipation.
→ turbulence; → decay.