INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS B: ATOMIC, MOLECULAR AND OPTICAL PHYSICS J. Phys. B: At. Mol. Opt. Phys. 39 (2006) 2145–2158 doi:10.1088/0953-4075/39/9/004 B-spline calculations of oscillator strengths in neutral argon Oleg Zatsarinny and Klaus Bartschat Department of Physics and Astronomy, Drake University, Des Moines, IA 50311, USA E-mail: oleg zoi@yahoo.com and klaus.bartschat@drake.edu Received 1 February 2006, in final form 28 March 2006 Published 18 April 2006 Online at stacks.iop.org/JPhysB/39/2145 Abstract 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. 1. Introduction Transition probabilities in the rare-gas atoms are well known to be important for both fundamental and practical reasons. The latter include modelling applications in the lighting and laser industry, plasma processing, and the interpretation of astrophysical data. A wealth of numerical data exists for the oscillator strengths of the Ar I spectrum. Numerous emission intensity measurements, performed mostly with stabilized arcs, as well as some lifetime determinations, have been reported in the literature. Early results may be found in the critical data compilations by Wiese et al (1969). Most of the work on Ar I has centred on the prominent red and blue lines, i.e., the 4s–4p and 4s–5p transition arrays, and the transition probabilities included in the NIST database for these transition arrays have been critically reanalysed by Wiese et al (1989). More recently, absolute oscillator strengths in noble gases have been obtained from photoabsorption spectra by Chan et al (1992) and from self-absorption of resonance radiation by Gibson and Risley (1995) and Ligtenberg et al (1994). Spectra 0953-4075/06/092145+14$30.00 © 2006 IOP Publishing Ltd Printed in the UK 2145