Kinetic energies of Ta-n(+) and Nb-n(+) ions (1 less than or equal to n less than or equal to 10) sputtered from pure Ta and Nb targets by 6 keV per atom Au-, Au-2(-) and Au-3(-) primary ions have been compared after energy spectra of these ions were recalibrated using a newly developed data processing algorithm. Most probable and mean energies were determined for the sputtered ions, and their energy spectra were converted into distributions over inverse velocities. Distributions obtained for Ta and Nb displayed many similarities and no principal differences. The only differences seen were due to the difference in masses of the elements. On the other hand, strong differences were observed between results for atomic and diatomic sputtered ions and those for larger sputtered cluster ions (with more than seven atoms). The comparison of atomic and polyatomic bombardment showed dramatic changes in emission of atomic and diatomic sputtered species, and almost no differences for larger sputtered clusters. (C) 2004 Elsevier B.V. All rights reserved.