X-ray　yields　for　the　projectile　L-shell　have　been　measured　for　collisions　between　Xe20+　and　thick　solid　targets　throughout　the　periodic　table　with　incident　energies　near　the　Bohr　velocity.　The　yields　show　a　very　pronounced　cyclic　dependence　on　the　target　atomic　number.　This　result　indicates　that　Xe　L　x-ray　emission　intensity　is　greatly　enhanced　either　in　near-symmetric　collisions　or　if　the　binding　energy　of　the　Xe　M-shell　matches　the　L-　or　N-shell　binding　energy　of　the　target.