Wave functions and oscillator strengths of Be-like ions (Be I, C III, N IV, O V)

Abstract

Several excited states of Be-like ions (Be I, C III, N IV, O V) are calculated by the Roothaan version of the Hartree-Fock method, namely 2 s 2 1 S, 2 s 2 p 1,3 P, 2 s 3 s 3 S, 2 s 3 p 1,3 P, 2 s 3 d 1,3 P. Eigenvalues and energies are given in Table 2. The wave functions (Tables 6 to 10) are given as sums over exponentials multiplied by a suitable power of r (Slater type wave functions). Tables 4 and 5 show orthogonality integrals. Oscillator strengths (Tables 11 to 14) are calculated with dipole length and dipole velocity formula, with experimental and with theoretical energy differences. For triplet transitions the results seem fairly reliable, while for singlet transitions there are large deviations between the ƒ-values calculated by dipole length and dipole velocity formula. Configuration mixing should be taken into account in these cases. ƒ-Values calculated with wave functions of different degree of accuracy show that the discrepancy between dipole length and dipole velocity values is insensitive towards the quality of the Hartree-Fock wave functions. Table 15 compares the line strengths calculated here with the values of Kelly (8). It shows satisfactory agreement.