Spectrum of Th-Ar Hollow Cathode Lamps, Line Lists

The line lists used in the atlas are taken from several sources as follows:

Th I-III

Thorium lines were taken from Table VI of Redman, Nave & Sansonetti (2014). This paper is a compilation of thorium lines taken from the following publications listed in the “Source” column. The wavenumbers have been modified as described in Section 4 of RNS13. The optimized Ritz wavelengths generally have much smaller uncertainties than the measured values and should be used unless the plots indicate that the observed line is blended. In this case, the blended lines should either be ignored or carefully modeled using the Ritz wavelengths.

• RNS13: Redman, Nave & Sansonetti (2014). The wavenumbers and uncertainties in this paper have been included without change.
• PE83: Palmer & Engleman (1983). Systematic trends in the wavenumbers of these spectra were removed as described in RNS13. These trends are small and thus have not been corrected in the plots. The uncertainties have been adjusted as described in RNS13.
• GBCZ74: Giacchetti et al. (1974). The wavenumbers in this paper have been included without change and have been assigned an uncertainty of 0.0034 cm^-1 as described in RNS13.
• ZC74: Zalubas & Corliss (1974). The wavenumbers in this paper have been included without change. The  uncertainties of the measured wavenumbers vary from 0.0037 cm^-1 for wavenumbers smaller than 10000 cm^-1 to 0.014 cm^-1 for wavenumbers greater than 10000 cm^-1, as described in RNS13.
• KNS08: Kerber et al. (2008). The wavenumbers and uncertainties in this paper have been included without change.
• LP07: Lovis & Pepe (2007). Wavenumbers from this paper have been included without change, but with uncertainties increased as described in RNS13.
• EHW03: Engleman, Hinkle, & Wallace (2003). Wavenumbers from this paper have been included without change. The uncertainties have been estimated using equation 7 of RNS13.
• Z76:  Zalubas (1976). The wavenumbers below 10800 cm^-1 in this paper have been increased by 0.0025 cm^-1 as described in RNS13. The uncertainties of the measured wavenumbers vary from 0.0026 cm^-1 for wavenumbers smaller than 10800 cm^-1 to 0.01 cm^-1 for wavenumbers greater than 10000 cm^-1, as described in RNS13.

Ar I

An analysis of the spectrum of Ar I was done by Whaling et al. (2002). Sansonetti (2007) found that their wavenumbers were too large by about 7 parts in 10⁸, and that more accurate values were present in an unpublished list widely circulated in the late 1990s. We have thus taken the Ar I wavenumbers from this unpublished list. Uncertainties for the measured wavenumbers are also taken from this list. Since the Ar I energy levels have not been optimized from Whaling et al.’s measurements, no Ritz wavenumbers are given for these lines.

Ar II, III

Ritz wavenumbers and uncertainties for Ar II and Ar III were taken from Table 1 of Whaling et al (1995) (95Wha in the ‘Source’ column) and have not been modified. This table reports the difference between the observed wavenumber and the Ritz wavenumber, but uncertainties of the observed wavenumbers are not given. We have thus calculated the observed wavenumber from the difference and have estimated the uncertainty (U_wn) of their observed wavenumbers W_n from their intensities (I_n) and widths (Fw_n) using:

U_wn  = sqrt( 0.25 x Fw_n²/I_n² +10^-16 x W_n²)

Ne I

Ne I lines are only present in the 75 mA spectrum from Palmer & Engleman (1983). Observed wavenumbers and uncertainties of Ne I lines have been taken from the compilation of Saloman & Sansonetti (2004) without change. Ritz wavenumbers were derived from their energy levels. The uncertainties were calculated by adding the uncertainties of the energy levels in quadrature. These data were taken from 13 of the 19 sources in Table 1 of Saloman & Sansonetti (2004); the remaining 6 sources contain solely data outside the wavelength region of the current atlas.

Ne II, III

Ne II and Ne III lines are only present in the 75 mA spectrum from Palmer & Engleman (1983). Observed and Ritz wavenumbers and their uncertainties were taken from the compilation of Kramida & Nave (2006) without change.