Journal of Physical Chemistry B, Vol.103, No.47, 10425-10432, 1999
Collision dynamics and decomposition of NaCl nanometer particles on hot platinum surfaces
The collision dynamics of nanometer size NaCl particles on hot (1200-1500 K) Pt surfaces are investigated with molecular beam techniques. A beam of particles with diameters of 15-80 nm is directed toward a polycrystalline Pt surface with a velocity of 260 m/s, The scattered flux is measured with a rotatable surface ionization detector that allows for counting and size determination of individual particles. The particle-surface interaction is highly inelastic, and angular distributions indicate that the scattered particles lose more than 90% of their kinetic energy in the surface normal direction. Particles also stick to the surface, and the sticking probability is strongly influenced by the incident particle velocity in the range 200-400 m/s. Particles deposited on the surface subsequently melt and decompose by evaporation of NaCl molecules. A small fraction of each deposited particle also gives rise to a pulse of desorbing Na+ ions, produced by surface ionization, which is used to monitor the decomposition process. The dynamics of the scattering, sticking, and decomposition processes are discussed, and the experimental findings are compared with results from earlier studies of clusters and micrometer-sized particles.
Keywords:MASS-SPECTROMETRY;GRAPHITE SURFACE;SCATTERING;CLUSTERS;IONIZATION;IMPACT;ENERGY;DESORPTION;SPHERES;CONTACT