= Jim Peebles
{c}
{tag=Physicist}
{wiki}
= P. James Peebles
{c}
{synonym}
= P. J. E. Peebles
{c}
{synonym}
= James Peebles
{c}
{synonym}
<Jim Peebles> calculated the recombination history of the early cosmic <plasma>. His treatment followed how <electrons> and <protons> form neutral <hydrogen> while the expanding background changes the conditions for atomic transitions.
An equilibrium abundance alone is insufficient when photons from atomic transitions are repeatedly reabsorbed and the expansion competes with reaction rates. Following this nonequilibrium history helps determine when the <cosmic microwave background> ceases to scatter efficiently. The calculation connects atomic <physics> to the observable last-scattering epoch.<Recombination of the Primeval Plasma by P. J. E. Peebles>[Abstract and opening kinetic discussion: non-equilibrium recombination and cosmological radiation]{ref}
\Image[https://commons.wikimedia.org/wiki/Special:Redirect/file/Jim_Peebles_(cropped_2).jpg?width=260]
{title=Portrait of <Jim Peebles>}
{description=Juan Diego Soler; 17 May 2010; existing Commons crop and levels adjustment by WikiPedant. https://creativecommons.org/licenses/by/2.0/[CC BY 2.0], via Wikimedia Commons.}
{source=https://commons.wikimedia.org/wiki/File:Jim_Peebles_(cropped_2).jpg}
{width=260}
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