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:
“Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.”
—Konrad Lorenz (1903–1989)
“Until, accustomed to disappointments, you can let yourself rule and be ruled by these strings or emanations that connect everything together, you haven’t fully exorcised the demon of doubt that sets you in motion like a rocking horse that cannot stop rocking.”
—John Ashbery (b. 1927)