Muonium atom spin exchange with alkali-metal vapors: Mu+Cs

Abstract

The thermally averaged total electron spin-flip cross sections (${\mathrm{\ensuremath{\sigma}}}_{\mathrm{SF}}$) for Mu-Cs have been measured in a 2 atm ${\mathrm{N}}_{2}$ moderator at 543, 566, and 643 K using the muon-spin-rotation technique. Within an overall experimental error of \ifmmode\pm\else\textpm\fi{}15%, the measured cross sections can be taken as temperature independent, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{SF}}$=39.7\ifmmode\pm\else\textpm\fi{}6.0\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}16}$ ${\mathrm{cm}}^{2}$, though there may be a trend to decreased values at the lower temperatures. This average value is considerably lower than either the early calculated results of Dalgarno and Rudge [Proc. R. Soc. London Ser. A 286, 519 (1965)] or the more recent ones of Cole and Olson [Phys. Rev. A 31, 2137 (1985)] for the corresponding H-Cs collisions, indicating a dramatic isotope effect.