Highly polarized muonic He produced by collisions with laser optically pumped Rb

Abstract

We have formed highly polarized muonic helium by stopping unpolarized negative muons in a mixture of unpolarized gaseous He and laser polarized Rb vapor. The stopped muons form muonic He ions which are neutralized and polarized by collisions with Rb. Average polarizations for $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ of (26.8\ifmmode\pm\else\textpm\fi{}2.3)% and (44.2\ifmmode\pm\else\textpm\fi{}3.5)% were achieved, representing a tenfold increase over previous methods. Relevant cross sections were determined from the time evolution of the polarization. Highly polarized muonic He is valuable for measurements of the induced pseudoscalar coupling ${\mathit{g}}_{\mathit{p}}$ in nuclear muon capture.