Evolution of the spectral region centered on the rest wavelength of Hα for model mdot0p01/rcsm2e14. The symmetric solid vertical lines on each side of the origin correspond to the velocity at the location in the unshocked CSM where the electron-scattering optical depth is 0.01. The dashed vertical lines correspond to ±V_∞, where V_∞ is the terminal wind velocity of the original, unadulterated CSM.