Lifetimes of Rydberg states in ions of the group II elements

Total probabilities A _nl of spontaneous radiative transitions, which determine lifetimes τ _nl = 1/A _nl of nS-, nP-, nD- and nF-states in singly charged ions of the group IIa (Be⁺, Mg⁺, Ca⁺, Sr⁺, Ba⁺) and IIb (Zn⁺, Cd⁺, Hg⁺) elements, were calculated in the single-electron Fues’ model potential (FMP) method. An asymptotic dependence is determined for highly excited states with small angular momentums and presented in the form τ _nl = τ _l ⁽⁰⁾ n ³ Q _l (1/n) and numerical values of the factors τ _l ⁽⁰⁾ and coefficients of the cubic polynomial Q _l (x) are calculated, which approximate results of numerical computations with relative error below 2% in the range of states with principal quantum numbers from n = 7 to n ≈ 2000. The comparison of the numerical results with data in literature is presented, and applicability and reliability of single-electron model calculations are discussed in detail for positive singly charged ions of the group II elements.