8.7 The emission spectrum of the Het ion contains the Pickering series of spectral lines that is analogous to the Lyman , Balmer and Paschen series in the spectrum of hydrogen . Balmer i = 1,2, ... 0.456806 0.616682 0.690685 0.730884 Pickering i = 1, 3, ... 0.456987 0.616933 0.690967 0.731183 The table gives the frequencies (in 10 15 Hz ) of the first four lines of the Balmer series and the first four odd -numbered lines of the Pickering series . The frequencies of alternate lines in the Pickering series are almost coincident with the frequencies of lines of the Balmer series . Explain this finding . Provide a quantitative explanation of the small offset between these nearly coincident lines in terms of the reduced mass of the electron in the two systems