Exact energy-eigenstates of the Coulomb-Stark Hamiltonian

An approximation-free, numerically efficient algorithm is presented for the Hamiltonian eigen-states of the Stark-Hydrogen problem describing a quantum particle exposed to the central Coulomb force and a homogeneous external field. As an example of application in a state-expansion with continuous energy, we calculate the time-dependent wavefunction of an electron tunneling from a hydrogen atom suddenly exposed to an external electric field.