Two-body $P$-state energies at ${\alpha }^6$ order

Vojtěch Patkóš, Vladimir A. Yerokhin, Krzysztof Pachucki

We present an analytical calculation of the complete ${\alpha }^6$ correction to energies of $nP$-levels of two-body systems consisting of the spin-$0$ or $1/2$ extended-size particles wit…