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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 ...
As a result, only three spectral lines will be visible, corresponding to the =, selection rule. The splitting Δ E = B μ B Δ m l {\displaystyle \Delta E=B\mu _{\rm {B}}\Delta m_{l}} is independent of the unperturbed energies and electronic configurations of the levels being considered.
This ambiguity about the underlying physical mechanism at work can be overcome by considering two-particle correlation functions (such as Auger electron spectroscopy and appearance-potential spectroscopy), as they are able to describe the collective mode of the system and can also be related to certain ground-state properties. [24]
For absorption spectra, the vibrational coarse structure for a given electronic transition forms a single progression, or series of transitions with a common level, here the lower level v″ = 0. [6] There are no selection rules for vibrational quantum numbers, which are zero in the ground vibrational level of the initial electronic ground ...
Using the selection rules, the hyperfine pattern of = transition and higher dipole transitions is in the form of a hyperfine sextet. However, one of these components ( Δ F = − 1 {\displaystyle \Delta F=-1} ) carries only 0.6% of the rotational transition intensity in the case of J = 2 → 1 {\displaystyle J=2\rightarrow 1} .
In rotational-vibrational and electronic spectroscopy of diatomic molecules, Hund's coupling cases are idealized descriptions of rotational states in which specific terms in the molecular Hamiltonian and involving couplings between angular momenta are assumed to dominate over all other terms.