Revised analysis of triply ionized argon (Ar IV)

The spectrum of three times ionized argon (Ar IV), has been observed in the 280-5000 Å wavelength range. In the previously reported energy level system for the 3 s 3 p 4 , 3 s 2 3 p 2 3 d and 3 s 2 3 p 2 4 s configurations, three levels were rejected, J -values of two levels were altered and LS -designations of eight levels were revised. Eight new levels have been added to the even parity system, completing 36 energy level values for the 44 possible levels of these even configurations. We also confirm 20 of the 21 previously reported levels for the 26 possible of the 3 s 2 3 p 3 and 3 s 2 3 p 2 4 p configurations. The configurations are interpreted by fitting the theoretical energy expressions to the observed energy levels using a least-square-fitting technique. 214 lines have been identified as transitions between the studied levels. For 112 of them the classification is new.