Orbital angular momentum in triatomic molecules

Abstract

The effects of orbital angular momentum on the details of the spin and rotational fine structure of the [Xtilde] ² B ₁ and à ² A ₁ states of NH₂ and H₂O⁺ are considered. It is found that the erratic spin-orbit splittings and asymmetry parameters of the à ² A ₁ states can be reproduced with good accuracy by calculations that also account for the regular spin and rotational structures of the ground states; the only input parameters are the shapes of the Born-Oppenheimer potential curves, the bond lengths and the spin-orbit coupling constants. The same calculations give an almost quantitative explanation of various perturbations in the à ² A ₁ state of NH₂. These perturbations are caused by the ground state and result from the presence of orbital angular momentum. Three types have been documented; one is direct spin-orbit interaction between the à and [Xtilde] states, and the others involve rotational asymmetry, which is found to be an important mechanism for causing perturbations between electronic states.

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Notes on contributors

Ch. Jungen

On leave (1976-77) at the Department of Chemistry, University of British Columbia, Vancouver, B.C., Canada.