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: 3 Search : selection
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.

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.

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.