Diagnostics of mixed van der Waals clusters

We present two complementary techniques that provide detailed diagnostics of supersonic beams involving several species. First, surface scattering, together with quadrupole mass spectrometer detection, yields the monomer percentage for each species within the beam. Second, analyses of beam profiles for different masses after scattering by a buffer gas permit determination of mixed cluster presence and, if any, of cluster sizes and compositions. The two techniques are applied to supersonic expansions of an argon-nitrogen mixture. We discuss the results that provide new insight in binary nucleation processes. Received: 6 October 1997 / Revised: 4 November 1997 / Accepted: 13 November 1997