For a potential which only depends on the magnitude of r, |r|, the operators L² and L_z commute with the hamiltonian. The stationary states of the Schrodinger equation may thus be taken to be eigenvectors of L² and L_z as well. Writing the solution as psi(r,theta,phi) = R(r)Y_l^m(theta,phi), the function R(r) obeys a radial Schrodinger equation. It is customary to write R(r)=u(r)/r, where the function u(r) can be shown to obey the one dimensional Schrodinger equation for r>0 with an effective potential energy equal to the original potential energy plus a term due to the kinetic energy in the theta and phi directions. For small r, u(r) behaves like r^l+1 so u(0) = 0.