(Color online) Energy levels (W) as function of relativity ( α 2 / 4 ) and the two-body parameter μ / m . The quantum numbers are l (orbital angular momentum) and n (radial nodes). From top: Purple lines: l = 2, n = 0. Solid line corresponds to equal masses, dashed line to the single mass limit. Green lines: l = 0, n = 1. Solid line corresponds to equal masses, dashed line to the single mass limit. Red, black respectively blue lines: l = 1, n = 0: μ / m = 0.25 (equal masses), = 0.125 (in between), respectively = 0 (single mass). Red, black respectively blue lines: l = 0, n = 0: μ / m = 0.25 (equal masses), = 0.125 (in between), respectively = 0 (single mass).