A series of lines in the spectrum of neutral Li atoms rise from combinations of 1s²2p^{1 2}P with 1s²nd^{1 2}D and occur at 610.36nm, 460.29nm, and 413.23nm. The d orbitals are hydrogenic. It is known that the 2P term lies at 670.78nm above the ground state, which is 1s²2s^{1 2}S. Calculate the ionization energy of the ground-state atom.