Line width for the −47 km s⁻¹ velocity component (or the sum of blended −47 and −38 km s⁻¹ components) as a function of principal quantum number. The red points show the measured line widths from this work (Table 1); the Cα(467) and Cβ(590) are derived only from the −47 km s⁻¹ velocity component, while the higher order transitions represent a single fit to the blended −47 and −38 km s⁻¹ components. The cyan triangles show the line widths of the Cα and Cβ transitions of the −47 km s⁻¹ velocity component from S17. The purple diamonds show the line widths of the −47 km s⁻¹ component from O17. The purple squares show the Cα, Cβ, Cγ and Cδ data, for which the −47 and −38 km s⁻¹ components are blended, from Stepkin et al. (2007). The colored lines show the contribution from Doppler broadening (yellow line), pressure broadening (green line), and radiation broadening (blue lines). The solid black line shows the model that best fit the line-widths from S17: a Doppler line width of 3.4 km s⁻¹, T_e = 85 K, n_e = 0.04 cm⁻³ and a radiation field that is a combination of a power law with T_r, 100 = 800 K and α = −2.6 plus a contribution to the radiation field from Cas A.