Asymptotically exact calculation of the exchange energies of one-active-electron diatomic ions

What is it about?

The surface integral method: We present a general procedure based on the Holstein-Herring method. for calculating exactly the leading term in the exponentially small exchange, energy splitting between two asymptotically degenerate states of a diatomic molecule or molecular ion. The general formulae we have derived are shown to reduce correctly to the previously known exact results for the specific cases of the lowest Sigma and Pi states of H(2)(+). We then apply our general formulae 2 to calculate the exchange energy splittincys between the lowest states of the diatomic alkali cations K(2)(+), Rb(2)(+) and Cs(2), which are isovalent to H(2)(+). Our results are found to be in very good agreement with the best available experimental data and ab initio calculations.

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Photo by Google DeepMind on Unsplash

Photo by Google DeepMind on Unsplash

Why is it important?

This is a general method for accurately calculating the elusive exchange energy splittings between the lowest discrete states of any one-active electron diatomic molecule (an electron shared by 2 effective neutral atoms, the hydrogen molecular ion being the simplest). This is the Holstein-Herring method made into a general calculation procedure applied to a number of successful benchnarks.

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