In a sample of H-atoms in ground state electrons make transition from ground state to a particular excited state where path length is 5 times de Broglie wavelength , electrons make back transition to the ground state producing all possible photons. If photon having 2nd highest energy of this sample can be used to excite the electron in a particular excited state of `Li^(2+)` ion then find the final excited state of `Li^(2+)` ion .