Upper panel: Normalized intensity profiles. Lower panel: Temperature (left y-axis) and density (right y-axis) for the pixels in sunspot umbra (left panel) and quiet Sun (right panel) marked by blue crosses in Fig. 2. SU0: strong emission feature in sunspot umbra; SU1: weak emission feature in sunspot umbra; QS0: strong emission feature in granule; QS1: weak emission feature in intergranular lane. Two optical depth scales are used in the lower panel, where optical depth, τ, scales at the peak wavelength of the Mg I 12.32 μm line intensity (lower x-axis), and τ₅₀₀ is the continuum optical depth at λ = 500 nm (upper x-axis). Note that the scale of τ₅₀₀ is uneven.