Control and characterization of the nucleation process during co-expansion of ternary mixtures
Laboratoire de Physique des Interfaces et des Couches Minces, CNRS, École Polytechnique, 91128 Palaiseau Cedex,
Published online: 15 September 2001
In this paper, we show how the use of a third non-condensable species gives both new insight and control on the binary nucleation process during supersonic expansion of gas mixtures. We present the case of an oxygen-nitrogen mixture diluted in various proportions of helium. Using beam diagnostics, we determine the mean cluster composition and size as well as the percentage of uncondensed matter present in the beam. The presence of helium permits us to understand the cooling and clustering role played by each species during the expansion process. We discuss, in particular, its influence on the dramatic composition change observed at the nucleation onset.
PACS: 36.40.-c – Atomic and molecular clusters / 68.03.Fg – Evaporation and condensation / 68.49.Fg – Cluster scattering from surfaces
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001