Observation of transitions involving core-excited states in Ar III and Ar IV and high-lying singly excited states in Ar I-Ar IV

In this paper we present a comprehensive analysis of beam-foil and beam-gas excited spectrum of argon observed in small wavelength region, 2965-3090 Å, using Ar+/2+ ions in the energy range 200-650 keV. The comparison of beam-foil spectrum (BFS) at different incident beam energy and with that of beam-gas spectrum (BGS), one can find solution for blending problem in beam-foil spectroscopy. Many new transitions were identified on the basis of calculated wavelength from the accurately known energy levels of Ar I, Ar II, Ar III and Ar V. The transitions of Ar I originate from highly excited states (10p to 17p and 10f to 17f). Based on TOPbase estimates using close-coupling approximation five transitions involving core-excited states and nine transitions originating from highly excited states in the spectrum of Ar III and Ar IV were also identified. Radiative life time of two core excited quintet states (3s3p4(4P)6d 5D and 3s3p4(4P)8f 5Fo) of Ar III were measured and found to be in 'good' agreement with that of the calculated value using close-coupling approximation.

► Beam-foil and beam-gas excited spectrum of Ar observed using Ar+/2+ ions at low energy. ► Many new transitions identified in the spectrum of Ar I, Ar II, Ar III and Ar V. ► The new transitions assigned based on wavelength calculated from known energy levels. ► The transitions also assigned based on TOPbase estimates using close-coupling approximation. ► The life time of core-excited 2 transitions in Ar III involving quintet states measured.