The Ionization Rate During the Decoupling Period in a Universe with Nonzero Cosmological Constant

Nonzero cosmological constant favours cosmological models with larger Hubble constant. The evolution of ionization during decoupling period in a universe with nonzero cosmological constant is computed by using a corrected recombination coefficient. Also presented in this paper is the redshift distribution of the last scattering surfaces of the cosmic background photons while the cosmological constant is nonvanishing. Finally, we give a brief estimation about the influence of He on the last scattering surfaces.