In physics and chemistry a selection rule, or transition rule, formally constrains the possible transitions of a system from one state to another. Selection rules have been derived for electronic, vibrational, and rotational transitions. The selection rules may differ according to the technique used to observe the transition.
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Famous quotes containing the words selection and/or rule:
“When you consider the radiance, that it does not withhold
itself but pours its abundance without selection into every
nook and cranny”
—Archie Randolph Ammons (b. 1926)
“In a country where misery and want were the foundation of the social structure, famine was periodic, death from starvation common, disease pervasive, thievery normal, and graft and corruption taken for granted, the elimination of these conditions in Communist China is so striking that negative aspects of the new rule fade in relative importance.”
—Barbara Tuchman (1912–1989)