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: 7 Search : select
Parkes Selected Region (PSR)
  ناحیه‌ی ِ گزیده‌ی ِ پارکس   
nâhiye-ye gozide-ye Parkes

Fr.: Région sélectionnée de Parkes   

A catalog of 397 radio sources between declinations +20° and +27° which were compiled from a finding survey made at 635 MHz with the 64m radio telescope at the Australian National Radio Astronomy Observatory, Parkes, N.S.W. and published in 1968. Originally abbreviated PSR, this catalog, which is also called PKS, replaces and improves on four earlier lists (1964 to 1966).

Parkes, proper noun; selected, p.p. of → select; → region.

rigorous selection rule
  رزن ِ گزینش ِ فرسخت   
razan-e gozineš-e farsaxt

Fr.: règle de sélection rigoureuse   

A → selection rule obeyed by → discrete transitions. Among them are: rigorous selection rules for → electric dipole transitions (→ permitted) requiring: 1) ΔJ must be 0 or ± 1 with J = 0 ↔ 0 forbidden. 2) ΔMJ = 0, ± 1. 3) → Parity change, i.e. even ↔ odd.

rigorous; → selection; → rule.

select
  گزیدن   
gozidan (#)

Fr.: sélectionner, choisir   

To choose from among several.

From L. selectus, p.p. of seligere "to choose out, gather apart," from se- "apart" + legere "to gather, select."

Gozidan "to select, choose;" Mid.Pers. vicitan, wizidan, wizin- "to choose, select, discriminate," related to cin-, cidan "to gather, collect;" Av. vicidāi- "to discern," viciθa- "separation, discernment;" from vi- "apart, away from" (O.Pers. viy- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + kay- "to choose;" cf. Skt. ci- "to gather, heap up," cinoti "gathers."

selection rule
  رزن ِ گزینش   
razan-e gozineš

Fr.: règle de sélection   

Any of a set of rules specifying the relationships between the → quantum numbers that characterize the initial and final states of a quantum-mechanical system in a → discrete transition. Transitions that do not agree with the selection rules are called → forbidden and have considerably lower probability. There are several types of selection rules (→ rigorous selection rule, → LS coupling, etc.) for → electric dipole transition (→ permitted), → magnetic dipole (forbidden), electric → quadrupole (forbidden), etc.

Selection, verbal noun of → select; → rule.

selective absorption
  درشم ِ گزینشی   
daršam-e gozineši

Fr.: absorption sélective   

Absorption which varies with the wavelength of radiation incident upon an absorbing substance.

Selective, verbal noun of → select; → absorption.

selective scattering
  پراکنش ِ گزینشی   
parâkaneš-e gozineši

Fr.: diffusion sélective   

A type of scattering that occurs when certain → particles are more effective at scattering a particular → wavelength of light, as in → Rayleigh scattering.

selective; → scattering.

site selection
  گزینش ِ سیت   
gozineš-e sit

Fr.: sélection de site   

The process of choosing a site for an astronomical observatory based on meteorology, seeing conditions, and access to the site.

site; → selection.