The Zeeman effect on lines in the (1,0) band of the F⁴Δ- X⁴Δ transition of the FeH radical

We report measurements of the magnetic tuning and broadening of single rotational lines in the (1,0) band of the F⁴Δ-X ⁴Δ transition of FeH. Since the Zeeman effect of FeH in the lowest rotational levels of the ground X⁴Δ state has been measured previously, the present measurements provide information on g-factors for two upper state rotational levels. The Zeeman splitting in the Q(7/2) line of the (1,0) band of the F⁴Δ_7/2-X ⁴Δ_7/2 transition was successfully modeled using a phenomenological approach. The observation of Zeeman broadening in the corresponding R(7/2) line has also made it possible to extract an approximate g-factor for the J = 9/2 level of the F⁴Δ_7/2(ν = 1) vibronic state. The g-factors determined have been used to predict spectral patterns for numerous rotational lines in the F⁴Δ _7/2-X⁴Δ_7/2 system; these are compared with observed features in the sunspot umbral spectrum.