Absolute difference between the LP07 "?" lines and the closest known PE83 thorium lines. The smaller bump below about 0.05 cm ⁻¹ made us suspect that there was a population of thorium lines that were in PE83, but were misidentified by LP07 as new thorium lines. A wavenumber difference of 0.05 cm ⁻¹ is a wavelength difference of 0.008 nm at 400 nm and 0.025 nm at 700 nm.