Light-induced states of H and H-, shadow states, and the dressed potential

Light-induced ''bound'' states of atoms originate from the movement of poles of the multichannel scattering matrix on the Riemann energy surface. The appearance of additional ''bound'' states of the negative hydrogen ion, recently predicted in the high-frequency theory, is related to the motion of resonance poles that correspond to autoionizing states in the absence of the field. Various pole trajectories leading to light-induced states are described for photodetachment from a one-dimensional square potential well. Certain light-induced states in atomic hydrogen are discussed in relation to the spectrum of the dressed Coulomb potential