We have investigated the energy transfer dynamics of O, Ar, and CO2 scattering from the surfaces of hydrocarbon, fluorocarbon, and ionic liquids and from hydrocarbon and fluorocarbon 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 collision step in gas-surface interactions. 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 O, Ar, and CO2 were directed onto the surfaces, and velocity and angular distributions of inelastically scattered species were determined fromtime-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 impulsive scattering (IS) and thermal desorption (TD). The average final velocity of the IS component depended on the angle through which the incident atom or molecule was deflected, ? = 180� - (?i + ?f), and the IS velocity distribution could not be described in terms of a temperature. The TD products exhibited a cosine angular distribution about the surface normal and desorbed with a velocity distribution that was given by a Maxwell- Boltzmann distribution at the surface temperature. In light of the observed dynamics for the various projectiles scattering on qualitatively different surfaces, we appraise the applicability and value of the surface analog of the gas-phase kinematic analysis, known as the Newton diagram, which might in principle be used to obtain effective surface masses for collisions of gas-phase species with surfaces and thereby allow insight into the surface structure.

Comparative dynamics of O, Ar, and CO<sub>2</sub> scattering on liquid and self-assembled monolayer surfaces

245th National Meeting (2013)

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Comparative dynamics of O, Ar, and CO2 scattering on liquid and self-assembled monolayer surfaces

Comparative dynamics of O, Ar, and CO₂ scattering on liquid and self-assembled monolayer surfaces