Angular-distribution measurements ofKx-ray emission by 1-MeV/amu ions with6≤Z≤9following electron capture from helium

Abstract

Angular distributions have been measured for the projectile $K$ x rays emitted by highly ionized ions with $6\ensuremath{\le}Z\ensuremath{\le}9$ incident on helium at MeV/amu energies. Polarization fractions have been determined by analysis of the data to include systematic consideration of the angular-dependent detector efficiency. For incident bare nuclei, a polarization fraction of 24.7 \ifmmode\pm\else\textpm\fi{} 1%, independent of energy and projectile atomic number, was observed for $K$ radiation following electron capture to excited states. With incident one-electron ions, a $Z$-dependent polarization fraction was obtained, reaching a maximum of 40 \ifmmode\pm\else\textpm\fi{} 2% for oxygen ions. Lower-charge-state ions show decreasing values of $P$ and the angular distributions approach isotropy for $K$ x radiation from ${\mathrm{F}}^{+2}$ ions. For collisions of ${\mathrm{F}}^{+4}$ ions in argon, the Ar $K$ radiation is isotropic within 2% uncertainty.