A low‐pressure magnetically confined argon arc discharge was used in a mass spectrometer ion source to study low‐energy (0–100 eV) sputtering of polycrystalline copper. Target bombarding ion current densities ranged from 60–200 &mgr;A/cm2. Neutral particles were studied. Cu atoms and Cu2molecules were detected. The mass ratio of analyzed Cu2molecules to Cu atoms increased with bombarding ion energies to about 5½% at ion energies of 100 eV. Target voltages for appearance of Cu atoms and Cu2molecules were − 19 and − 50 V, respectively. No Cu3molecules were detected; if they were present, it was estimated that the ratio189Cu3to63Cu is less than 0.09%. The method has been found to be promising for the study of neutral particles in low‐energy sputtering. Yield curves agree well with results of other observers; sensitivities of 7×10−4atoms/ion were attained, and this figure can be improved.