Experimental investigation of the hyperfine structure of Tm I with Fourier transform spectroscopy, part A: In the visible wavelength range (400–700 nm)

The spectra emitted by a thulium hollow-cathode discharge lamp with argon or neon as inert gases have been recorded with a Bruker IFS 125 HR fourier transform spectrometer in the visible wavelength region from 400 to 700 nm. The paper presents the investigation of the hyperfine-structure splitting of 50 spectral lines of neutral thulium. As a result, the magnetic dipole hyperfine structure constant A for 20 fine structure levels of Tm I have been determined for the first time.