B-spline calculations of oscillator strengths in neutral argon

B -spline box-based multi-channel calculations of transition probabilities in Ar I are reported for energy levels up to n = 12. An individually optimized, term-dependent set of non-orthogonal valence orbitals is used to account for the strong term dependence in the one-electron orbitals. Energy levels and oscillator strengths for transitions from the 3p 6 ground-state configuration as well as for transitions between excited states have been computed in the Breit–Pauli approximation. The agreement in the length and velocity gauges of the transition data and the accuracy of the binding energies are used to estimate the accuracy of our results, which are also compared with experimental and other theoretical data. It is shown that the present method can be used for accurate calculations of oscillator strengths for states with intermediate and high n -values, for which it is difficult to apply standard multi-configuration Hartree–Fock methods.