Section of the Nd-Ar PDL FT spectrum (solid line) containing many 4f³6p–4f³(7s + 6d) transitions in its neighbourhood. The corresponding section of the Nd-Ar HCL spectrum is shown using the dash-dotted line. Six 4f³6p–4f³6d transitions of Nd III are marked, the two Ar lines were classified by comparison with observed lines of Saloman (2010); Kramida et al. (2023). The wavenumber of this section is above all Ritz wavenumbers of allowed E1 transitions between known energy levels of Nd I-II (Blaise et al. 1971, 1984; Martin et al. 1978; Kramida et al. 2023), and no classified Nd IV transitions (Wyart et al. 2007; Deghiche et al. 2015) matched the lines marked as ‘U’. Wavelengths and wavenumbers are given as vacuum values.