Hyperthermal Carbon Dioxide Interactions with Self-Assembled Monolayer Surfaces
Abstract
We have conducted new investigations of the energy transfer dynamics of CO2 scattering from fluorocarbon liquid and self-assembled monolayer (SAM) surfaces, using the direct comparison of the scattering behavior from the liquid and semi-solid surfaces to allow new insight into the pivotal initial step in gas-surface reaction dynamics. Specific interests are to probe the influence of surface structure vs. mass effects on the scattering dynamics and the role of the structure of the incident projectile. Molecular beams of CO2 were directed onto the surfaces, and velocity and angular distributions of inelastically scattered species were determined from time-of-flight distributions collected for various initial and final angles with the use of a rotatable mass spectrometer. All velocity distributions were bimodal and were interpreted in terms of two limiting cases of direct inelastic scattering (IS) and thermal desorption (TD). The average final velocity of the IS component depended on the deflection angle (x=180 deg - (theta(i) + theta(f)), and the IS velocity distribution could not be described in terms of a temperature. The more specular angular distributions for the IS products from the SAM surfaces suggest that the SAM surfaces are smoother than the liquid surfaces. Still, there is more energy transfer on the SAM surfaces, which is likely the result of significant deflection of SAM chains during the collision in comparison with molecular fragments on the liquid surfaces. We have demonstrated that a simple kinematic analysis that models the scattering as an incident sphere interacting with a sphere-like localized region of the surface with a finite effective mass describes the energy transfer well even though the incident species is a molecule with internal structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 08, 2013
- Accession Number
- ADA586232
Entities
People
- Timothy K. Minton
Organizations
- Montana State University