Abstract
SynopsisWe present short-range phase shifts and spin-exchange cross sections for elastic electron scattering from selected one-electron ions from He+ to Fe25+. The results are explained in a simple physical picture based on quantum defect theory.
Highlights
The signature of matter formation, the epoch of recombination, is recorded on the relic radiation, the cosmic microwave background (CMB)
A possible relic radiation from the reionization era could come from the hydrogen hyperfine 21-cm (1.420 GHz) tomography (Loeb & Zaldarriaga 2004), when the spin temperature of the 21-cm line (Ts) (Purcell & Field 1956) falls below that of the CMB radiation (Tcmb), rendering the high redshift 21-cm signal visible in the CMB
As seen from the figure, this expectation is very well fulfilled. It follows from Eq (3) that the phase shifts should fall off like 1/Z with increasing Z, and one would expect the SE cross section to scale like 1/Z2
Summary
The signature of matter formation, the epoch of recombination, is recorded on the relic radiation, the cosmic microwave background (CMB). This imprint occurred at the surface of last scattering, corresponding to a redshift of z ≈ 1100. Observations of Lyman-α (Ly-α) absorption at z ≈ 6 in quasars have pinned the end of the reionization epoch (Fan et al 2002). This epoch, called the cosmic reionization, is frontier astronomy, because there are few observational constraints on the nature of processes during this era. A possible relic radiation from the reionization era could come from the hydrogen hyperfine 21-cm (1.420 GHz) tomography (Loeb & Zaldarriaga 2004), when the spin temperature of the 21-cm line (Ts) (Purcell & Field 1956) falls below that of the CMB radiation (Tcmb), rendering the high redshift 21-cm signal visible in the CMB
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