The Interaction of Monatomic and Diatomic Molecules with Solid Surfaces: The Structure of Water Cluster Beams and Their Scattering from Surfaces.
Final rept. 1 Oct 78-30 Sep 80,
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS
Pagination or Media Count:
An experimental study of homogeneous and heterogeneous nucleation was conducted, using molecular beam techniques mass spectrometry and time-of-flight velocity spectrometry, with and without mass filtering. Both the clustered beam itself and the scattering of the clusters from surfaces were studied. The beam was found to consist of a broad spectrum of clusters all having approximately the same velocity distribution. Small clusters were found to have a binding energy much less than that of bulk ice. Measurements of a beam scattered from a surface using a time-of-flight velocity spectrometer show four distinct patterns. These are 1 a diffuse scattering channel monomers, Maxwelliancosine at the target temperature, 2 a direct inelastic channel for monomers characterized by a small loss of incident velocity with a broad spatial distribution peaked at the tangent for all incident angles, theta sub i, 3 a well-defined specular directed lobe theta sub s theta sub i greater than 50 deg with particle velocity much slower than 1 or 2 and a velocity distribution narrower than a stationary Maxwellian, and 4 another slow peak with a slightly broader velocity distribution into a sharp intensity peak near the tangent for all theta sub i greater than 50 deg. The amplitude of the specularly directed slow peak 3 appears to give a sensitive indication of surface coverage. Author
- Atomic and Molecular Physics and Spectroscopy