To limit inhomogeneous broadening from isotope variations, we started with compositions containing Eu 3+ , one or two mononuclidic cations, and a mononuclidic anion or oxygen. We excluded mononuclidic cations that are magnetic, toxic, radioactive, or in the lanthanides, leaving 12: Al 3+ , Au +/3+ , Bi 3+ , Cs + , Na + , Nb 5+ , P 3+/5+ , Rh 3+ , Sc 3+ , and Y 3+ . We included O 2-in addition to the mononu-clidic anions F -and I -to expand the initial search range. Oxygen should contribute little to broadening because of the high natural abundance of O and its low mass relative to the other elements. This process gives 234 ternary and quaternary combinations (eg. Eu 3+ -Cs + -Na + -F -). Adding quaternary oxyfluorides and iodates brings the total to 258 combinations.