Accurate Ritz wavelengths of parity-forbidden [FeII], [TiII] and [CrII] infrared lines of astrophysical interest
Context: With new astronomical infrared spectrographs the demands of accurate atomic data in the infrared have increased. In this region there is a large amount of parity-forbidden lines, which are of importance in diagnostics of low-density astrophysical plasmas. Aims: We present improved, experimentally determined, energy levels for the lowest even LS terms of Fe ii, Ti ii and Cr ii, along with