Strong fragmentation of large rare gas clusters by high energy electron impact

The interaction of large argon, krypton, and xenon clusters in the size range from [n] = 170 to 10,280 with electrons is investigated in a reflectron time-of-flight mass spectrometer. The clusters are generated in adiabatic expansions through conical nozzles and are nearly fragmentation-free detected by single photon ionization after they have been doped by one sodium atom. In contrast, using electron impact ionization, the clusters are nearly completely fragmented when varying the electron energy between 50 and 1500 eV. The operating mechanism is that which is also responsible for the electronic sputtering of solid matter. The yields, however, are orders of magnitude larger for clusters than for the solid. This result is a consequence of the finite dimensions of the clusters which cannot accommodate the energy. (C) 2002 Elsevier Science B.V. All rights reserved.