Identification of the 3p4(1D)5d2S term in Ar II

The position of the 3p 4 ( 1 D)5d 2 S term in Ar II has recently been discussed in connection with the 3s photoelectron satellite sum of Ar. The authors report the identification using optical spectroscopy of the 3p 4 ( 1 D)5d 2 S 1/2 level 216882.16 cm -1 above the ground level 3p 5 2 Pd 3/2 . This is approximately 2800 cm -1 below the position reported in a recent determination by Adam et al. (1978) using photoelectron spectroscopy. The difference is perhaps due to an admixture of unresolved higher nd 2 S terms in the photoelectron spectrum.