The energy needed to strip electrons from higher levels in the well is easily found. Due to conservation of energy , an atom can only absorb an amount of energy which just promotes an electron to a higher level. If the electron leaves the atom, the atom is ionized A comment about ionization. To ionize an atom, all we require is that the photon have enough energy to lift the electron out of the well. Such ionization edges are seen in the spectra of many stars.
Balmer lines fall in the optical .
Paschen, Brackett, and Pfund lines fall in the infrared .