Deviation between HFR and experimental wavelengths, Δλ/λ_Exp (Δλ = λ_HFR − λ_Exp) as a function of λ_HFR for spectral lines in Hf I–IV, Os I–IV, and Au I–IV ions. Experimental data were taken from Kramida et al. (2023) (NIST) for Hf I–II, Os III, and Au I; from Malcheva et al. (2009) for Hf III; from Sugar et al. (1974) for Hf IV; from Ivarsson et al. (2003) and Quinet et al. (2006) for Os I; from Ivarsson et al. (2004) and Quinet et al. (2006) for Os II; from Ryabtsev et al. (1998) for Os IV; from Ryabtsev et al. (1998) for Au II; from Zainab & Tauheed (2019) for Au III; and from Wyart et al. (1994) for Au IV.