Analytic formulae of atomic energy levels in high-temperature low-density plasmas

In this paper, analytic formulae are given to account for the plasma effect on the atomic energy levels using the Debye shielding potential. The formulae are obtained by using hydrogen-like wavefunctions. However, the present results agree well with those of the numerical method not only for hydrogen-like ions but also for multi-electron ions. The formulae are also useful to determine conveniently the maximum orbit of ions in plasmas.