The Interaction of Monatomic and Diatomic Molecules with Solid Surfaces: The Structure of Water Cluster Beams and Their Scattering from Surfaces.
Abstract
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, Maxwellian/cosine 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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1980
- Accession Number
- ADA093881
Entities
People
- David D. Dreyfuss
- Harold Y. Wachman
- Leon Trilling
Organizations
- Massachusetts Institute of Technology