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The Laporte rule is a rule that explains the intensities of absorption spectra for chemical species. It is a selection rule that rigorously applies to atoms, and to molecules that are centrosymmetric, i.e. with an inversion centre. It states that electronic transitions that conserve parity are forbidden. Thus transitions between two states that ...
The Laporte rule is a selection rule formally stated as follows: In a centrosymmetric environment, transitions between like atomic orbitals such as s-s, p-p, d-d, or f-f, transitions are forbidden. The Laporte rule (law) applies to electric dipole transitions, so the operator has u symmetry (meaning ungerade, odd).
The lattice must also be stable under chemical and photochemical conditions, as these are the environments the conversion will take place within. Finally, this host lattice ought to have low symmetry, allowing for a slight relaxation of the Laporte selection rules. The normally forbidden transitions lead to an increase in the f-f intermixing ...
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Near room temperature, these salts are yellow , but these solids become blue when heated to near 70 °C. The bright blue color is characteristic of tetrahedral [NiCl 4] 2−, the intensity being a consequence of the Laporte selection rule. The yellow color results from a polymer consisting of octahedral Ni centers.
WASHINGTON (Reuters) -U.S. President Donald Trump said on Tuesday the United Nations has "great potential" but has to "get their act together," as he stopped U.S. engagement with the U.N. Human ...