Аннотация:Two-photon resonant three-photon ionisation spectroscopy has been employed in measuring energies of Pb even-parity Rydberg levels. Data are presented for the energies of 71 bound states, most of which are from three Rydberg series, that is, 6pnp(1/2, 1/2)0, 6pnp(1/2, 3/2)2 and 6pnf 1/2(5/2)2. By fitting the new data obtained, basic parameters of multichannel quantum defect theory (MQDT) for the even-parity states have been determined. The Rydberg levels have been evaluated and compared with available experimental data. A good correspondence has been achieved. Strong perturbations between the Rydberg series have also been discussed.
