2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48320For the S-states of positronium and muonium, the terms of an expansion of energy levels in powers of the fine structure constant $α$ are also members of a "recoil series". The first two terms of that series are calculated to all orders in $α$.5 pages, latexHigh Energy Physics - Phenomenologytext