... Surveyor

www.rssd.esa.int/Planck

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... narrower

Our computations show that the broadening due to electron scattering is $\Delta\nu/\nu \lesssim 7\%$, so the overall width of the $He {\sc iii}\rightarrow He {\sc ii}$-features is still smaller than the cosmological hydrogen recombination lines (Rubino-Martin et al. 2007).

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