Keywords: 
• 主线系 /
• 精细结构 /
• 多体微扰理论(MBPT) /
• Breit效应

Abstract: The fine-structure intervals of Na principal series np（n = 3—9） are calculated by the many-body perturbation theory（MBPT） within the framework of relativity.To deal with the problem that a large set of continuum states is required in the MBPT calculation, an exponential potential is employed to generate a discrete,finite and nearly complete set of numerical basis functions.The zerothorder wavefunctions and eignvalues are obtained by solving the relativistic Hartree-Fock（RHF） equation and the RHF equation with the action of a potential barrier.The basis set used in this work contains intermediate orbitals with the angular momentum l≤6 and in an appropriate energy range,and most of them are the so called ＂contracted＂ orbitals.Encouraging results are obtained using this technique to calculate the second-order correlation corrections,combining the Breit effects in a first-order perturbation approach. Compared with other theoretical calculations,the present results are much close to the experimental results.