Chemical dynamics simulations were performed to understand mechanisms and energetics for protonated dialanine (ala2-H+) interacting with a perfluorinated self-assembled monolayer (F-SAM) surface. Collisions of ala2-H+ with the F-SAM were simulated for collision energies of 5, 13.5, 22.5, 30, and 70 eV and for incident angles of 0o (perpendicular to the surface) and 45o. Direct scattering was observed as well as adsorption, soft-landing (SL) events. The latter consisted of physisorption on the surface and also with penetration of the surface. Some of the ala2-H+ remained trapped on/in the F-SAM when the simulations were terminated. Excellent agreement with experiment was found for the collision energy transferred to the ala2-H+ vibrational and rotational degrees of freedom. Chemical dynamics simulations were also performed to determine the structure of adsorbed ala2-H+ on the F-SAM. These simulations were also used to determine the desorption rate constant versus temperature, and the Arrhenius A-factor and activation energy for desorption. The lifetime for ala2-H+ adsorption on the surface at 300 K was determined.

Dynamics of protonated dialanine adsorption on and desorption from a F-SAM surface

256th National Meeting (2018)

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