Role of k _G,λ(μ). The solid line is the model profile computed using pure R _{II- AD} type redistribution and k _G,λ(μ) determined from observations. The dotted line is the observed Q/ I in the nonmagnetic region (same as the solid line in the top panel of Figure  2). The dashed line is the model profile computed using pure R _{II- AD} type redistribution but with a flat k _G,λ(μ) = 0.112 for all wavelengths. The free parameters obtained from the model fit are S = 0.325, C = 9.7 × 10 ⁻⁵, and P _c = 0.25%.