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Rotational selection rules for doublet-quartet transitions in asymmetric top molecules

1978; Elsevier BV; Volume: 72; Issue: 2 Linguagem: Inglês

10.1016/0022-2852(78)90119-4

1096-083X

C. di Lauro, F. Lattanzi, Francesco Lelj,

Advanced Chemical Physics Studies

Abstract Selection rules on the rotational structure of doublet-quartet transitions in asymmetric top molecules are discussed on the basis of the spin-orbit coupling mechanism, rather than by symmetry arguments, and some additional rules are found with respect to a previous work. In the case that the combining doublet and quartet states are appreciably mixed only with levels directly connected to them by the spin-orbit operator, it turns out that, except for the very low values of the rotational quantum numbers, branches with |Δ N − Δ J | > 1 are essentially forbidden. Thus, branches with Δ N = ± 3 ( T and N branches) are not expected to be observable. In this case, it is found also that in a high magnetic field transitions with Δ M s = ±2 are forbidden, and only Δ M s = 0, ±1 bands are expected to occur. All these restrictions are removed if the combining states are also appreciably contaminated by states indirectly connected to them by the spin-orbit operator, through intermediate levels.