Photoelectrons are emitted when `400 nm` radiation is incident on a surface of work - function 1.9 eV. These photoelectrons pass through a region containing `alpha`-particles. A maximum energy electron combines with an `alpha` -particle to from a `He^+` ion, emitting a single photon in this process. `He^+` ions thus formed are in their fourth excited state. Find the energies in eV of the photons lying in the 2 to 4 eV range, that are likely to be emitted during and after the combination. `[Take, h = 4.14xx10^(-15) eV -s]`