Formula_18380

\[\left(H_{l}-k^{2}\right) \psi_{l} \equiv\left(-\frac{\partial^{2}}{\partial r^{2}}+\frac{l(l+1)}{r^{2}}-k^{2}\right) \psi_{l}(r, k)=0, \quad r, k \in \mathbb{R}^{l},\]