A sodium cluster ion, Na-9(+), having a closed electronic shell was allowed to collide with a rare-gas atom (He or Ne), and collisionally fragmented ions were measured by using a tandem mass-spectrometer equipped with several octapole ion guides. The mass spectrum of the product ions show that sodium atom and dimer are released dominantly from the cluster ion, Na-9(+). The dependencies of the absolute cross sections for the Na and the Na-2 release on the collision energy were determined for collision energies up to 3 eV in the center of mass frame. The cross section for the Na-2 release increases much more rapidly than that for the Na release as the collision energy increases, while the cross sections for the Na and the Na-2 release start to rise at almost the same collision energy of 0.75 +/- 0.1 eV. The collision-energy dependencies are explained by orbital correlation diagrams for the Na-8(+) + Na and the Na-7(+) + Na-2 systems on the basis of a model that a spherical jellium of Na-9(+) is deformed by collision of a rare-gas atom. The total absolute cross sections are estimated by a two-step scheme : collisional excitation and dissociation.