3D spherical infinite well: V(r<a) = 0 V(r>=a) = inf

Energy levels determined by the Radial function whose solution are the Bessel/Neumann functions. Neumann functions are discarded due to regularity requirement at r=0 Parameter of Bessel function k_nl can be found via boundary conditions at r=a, where Bessel function must be zero. E_nl = h_bar^2 k_nl^2 / (2ma^2)