Ridge regression energy levels calculation of neutral ytterbium (Z = 70)

In view of the difficulty in calculating the atomic structure parameters of high-Z elements, the Hartree–Fock with relativistic corrections (HFR) theory in combination with the ridge regression (RR) algorithm rather than the Cowan code’s least squares fitting (LSF) method is proposed and applied. By analyzing the energy level structure parameters of the HFR theory and using the fitting experimental energy level extrapolation method, some excited state energy levels of the Yb I (Z = 70) atom including the 4f open shell are calculated. The advantages of the ridge regression algorithm are demonstrated by comparing it with Cowan code’s LSF results. In addition, the results obtained by the new method are compared with the experimental results and other theoretical results to demonstrate the reliability and accuracy of our approach.