In the frame work of multi-channel quantum defect theory (MQDT), the energy levels of three even Rydberg series 4f13(2F7/2o)6s(7/2, 1/2)4onp3/2, 4f13(2F7/2o)6s(7/2, 1/2)3onp3/2 and 4f13(2F7/2o)6s(7/2, 1/2)3onp1/2 converging to 4f13(2F7/2o)6s(7/2, 1/2)4o or 4f13(2F7/2o)6s(7/2, 1/2)3o of thulium atom are calculated by relativistic multi-channel theory. Compared with the experimental data from National Institute of Standards and Technology (NIST), the theoretical result shows two different types of electron-correlation effects: 1)the interaction between two Rydberg series results in energy shifts for these Rydberg series; 2)an isolated perturbed state is embedded in the energy range of a Rydberg series and interacts with the whole series, and breaks the regularity of the Rydberg series, and quantum defects show a large jump around the perturbed state. More specifically, by comparing the present calculated quantum defects with the experimental data, we reassign two Rydberg series: 1)4f13(2F7/2o)6s(7/2, 1/2)4onp3/2 Rydberg series from NIST is reassigned as 4f13(2F7/2o)6s(7/2, 1/2)4onf5/2, J=(5/2)+, 4f13(2F7/2o)6s(7/2, 1/2)4onf5/2, J=(7/2)+ and/or 4f13(2F7/2o)6s(7/2, 1/2)4onp1/2, J=(9/2)+ Rydberg series, and the difference between experimental and calculated quantum defects is generally better than 0.1; 2)4f13(2F7/2o)6s(7/2, 1/2)3onp3/2 Rydberg series from NIST is reassigned as 4f13(2F7/2o)6s(7/2, 1/2)3onf7/2, J=(5/2)+, 4f13(2F7/2o)6s(7/2, 1/2)3onf7/2, J=(7/2)+ and/or 4f13(2F7/2o)6s(7/2, 1/2)3onf5/2, 7/2, J=(9/2)+ Rydberg series, and the difference between experimental and calculated quantum defects is generally better than 0.05. As for the 4f13(2F7/2o)6s(7/2, 1/2)3onp1/2 Rydberg series from NIST, we find there is a perturbed state at about 49900 cm-1, and assign the perturbed state as 4f13(3F4)6 d5/26s2, J=7/2 and the total angular momentum for the Rydberg series is J=7/2.
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