The Hamiltonian for a hydrogen-like potential can be written in spherical coordinates as H = 1 2 μ μ [ p r 2 + 1 r 2 L 2 ] + V ( r ) , where V ( r ) = − − Z e 2 / r , and the radial momentum p r = x r p x + y r p y + z r p z , which is real and self-conjugate.