In two-photon ionization spectroscopy, the combined energy of two different photons is used to remove an electron from an atom or molecule. In such an experiment, a potassium atom in the gas phase is ionized by two different lasers, one of which has a wavelength of 566.0 nm. What is the maximum wavelength for the second laser that will cause two-photon ionization? The ionization energy of potassium is 6.96E-19 J.