Physical Review A - Atomic, Molecular, and Optical Physics
Rydberg level energies for Li7 were measured using triple-resonance laser excitation, followed by drifted field ionization. In addition to the principal n P2 series, weak Stark mixing from residual electric fields allowed observation of n S2 and hydrogenic Stark manifold series at higher n. Limit analyses for the series yield the spectroscopic ionization energy EI (Li7) =43 487.159 40 (18) cm-1. The Li 6,7 isotope shift (IS) was measured in selected n P2 Rydberg levels and extrapolation to the series limit yields IS (EI) 7,6 =18 067.54 (21) MHz. Results are compared with recent theoretical calculations: EI values from experiment and theory agree to within 0.0011 cm-1, with the remaining discrepancy comparable to uncertainty in QED corrections of order α4 Ry. The difference between experiment and calculated mass-based IS (EI) yields a change in nuclear charge radii between the two isotopes δ r2 7,6 =-0.60 (10) fm2. © 2007 The American Physical Society.
Bushaw, B. A.; Nortershauser, W.; Drake, Gordon W. F.; and Kluge, H. J.. (2007). Ionization energy of Li 6,7 determined by triple-resonance laser spectroscopy. Physical Review A - Atomic, Molecular, and Optical Physics, 75 (5), 52503-1-52503-8.