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Rydberg level energies for 7 Li were measured using triple-resonance laser excitation, followed by drifted field ionization. In addition to the principal n 2 P series, weak Stark mixing from residual electric fields allowed observation of n 2 S and hydrogenic Stark manifold series at higher n. Limit analyses for the series yield the spectroscopic ionization energy E I ͑ 7 Li͒ = 43 487.159 40͑18͒ cm −1. The 6,7 Li isotope shift ͑IS͒ was measured in selected n 2 P Rydberg levels and extrapolation to the series limit yields IS͑E I ͒ 7,6 = 18 067.54͑21͒ MHz. Results are compared with recent theoretical calculations: E I values from experiment and theory agree to within 0.0011 cm −1 , with the remaining discrepancy comparable to uncertainty in QED corrections of order ␣ 4 Ry. The difference between experiment and calculated mass-based IS͑E I ͒ yields a change in nuclear charge radii between the two isotopes ␦͗r 2 ͘ 7,6 = −0.60͑10͒ fm 2 .

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