Spectral line properties also depend on the excitation potential: Synthetic Fe I lines for a “Solar G2 V” model. Top: plot of disk center (μ = cos θ = 1.0), three line strengths, and three excitation potentials χ = 1, 3, and 5 eV is shown. Bottom: same for disk position μ = cos θ = 0.59. The decreased intensity reflects the limb darkening at λ = 620 nm. Higher excitation lines tend to be shallower and broader although the exact properties depend on the detailed line formation for each transition.