The emission of negatively charged HfF n − (n ≤ 5) and WF n − (n ≤ 7) molecular ions sputtered from a mixed Hf-W-PbF 2 fluoride sample by a 13 keV Cs + ion beam was studied. The emitted ions were detected in a high-sensitivity double-focusing secondary ion mass spectrometer. In the HfF n − and WF n − series, HfF 5 − and WF 6 − are the anions formed most abundantly, with their ratio amounting to HfF 5 − /WF 6 − ∼6, whereas HfF 5 − /WF 5 − ∼18. In particular, the rather high yield of the HfF 5 − anion could be essential for the sensitive detection of live 182 Hf, a radionuclide (half-live ∼9 million years) that might originate from stellar events in the vicinity of the Earth. Generally, these high ion yields appear to correspond with a high electron affinity of the respective molecule. In addition, their formation may be affected by the atomic composition at the sputtering site. Because their constituents originate from (initially) separated sources (the individual Hf, W and PbF 2 particles), the production of the HfF n − and WF n − molecular anions is envisaged to require an extensive mixing between these different reservoirs during sputtering. Furthermore, the energy distributions of these molecular anion species indicate that they are released from the surface via a collision cascade that also leads to the occurrence of fragmentation processes in the emission event.