K-shell　X-ray　emission　of　Silicon　induced　by　near-Bohr-velocity　ions　was　systematically　investigated　in　collision　systems　for　which　the　ratio　of　projectile-to-target　atomic　numbers　(Z(1)/Z(2))　ranged　from　0.07　to　3.79.　The　results　show　that,　in　asymmetric　collisions,　the　measured　K-shell　X-ray　production　cross　sections　of　Silicon　fit　very　well　with　the　predictions　of　different　direct　ionization　models　depending　on　the　atomic　number　of　projectile.　In　the　case　of　near-symmetric　collisions　(Z(1)/Z(2)　similar　to　1),　an　obvious　enhancement　of　the　X-ray　production　cross　section　was　observed,　which　can　be　attributed　to　the　vacancy　transfer　within　the　framework　of　quasi-molecular　model.　(C)　2016　Elsevier　B.V.　All　rights　reserved.