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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 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 remaining two integrals contributing to the probability amplitude determine the electronic spatial and spin selection rules. The Franck–Condon principle is a statement on allowed vibrational transitions between two different electronic states; other quantum mechanical selection rules may lower the probability of a transition or prohibit ...
Angle-resolved photoemission spectroscopy is a potent refinement of ordinary photoemission spectroscopy. Light of frequency ν {\displaystyle \nu } made up of photons of energy h ν {\displaystyle h\nu } , where h {\displaystyle h} is the Planck constant , is used to stimulate the transitions of electrons from occupied to unoccupied electronic ...
Together with the selection rules for an electric dipole transition, i.e., =, =, =, =, this allows to ignore the spin degree of freedom altogether. As a result, only three spectral lines will be visible, corresponding to the Δ m l = 0 , ± 1 {\displaystyle \Delta m_{l}=0,\pm 1} selection rule.
The restriction of the spin selection rule makes it even easier to predict the possible transitions and their relative intensity. Although they are qualitative, Tanabe–Sugano diagrams are very useful tools for analyzing UV-vis spectra: they are used to assign bands and calculate Dq values for ligand field splitting.
In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate electronic energy levels and the resulting splittings in those electronic energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the nucleus and electron clouds.
The conservation of angular momentum leads to selection rules, i.e., rules defining which multipoles may or may not be emitted in particular transitions. To make a simple classical comparison, consider the figure of the oscillating dipole.