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Helium energy levels including $m \alpha^6$ corrections

Krzysztof Pachucki
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Abstract

The $m \alpha^6$ correction to energy is expressed in terms of an effective Hamiltonian $H^{(6)}$ for an arbitrary state of helium. Numerical calculations are performed for $n=2$ levels, and the previous result for the $2^3P$ centroid is corrected. While the resulting theoretical predictions for the ionization energy are in moderate agreement with experimental values for $2^3S_1$, $2^3P$, and $2^1S_0$ states, they are in significant disagreement for the singlet state $2^1P_1$.

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Krzysztof Pachucki. 2006-10-17. Helium energy levels including $m \alpha^6$ corrections. https://doi.org/10.1103/physreva.74.062510

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