Scattering, accommodation, and trapping of HCl in collisions with a hydroxylated self-assembled monolayer.

Time-of-flight molecular beam scattering techniques are used to explore the energy exchange, thermal accommodation, and residence time of HCl in collisions with an OH-terminated self-assembled monolayer. The monolayer, consisting of 16-mercapto-1-hexadecanol (HS(CH(2))(16)OH) self-assembled on gold, provides a well-characterized surface containing hydroxyl groups located at the gas-solid interface. Upon colliding with the hydroxylated surface, the gas-phase HCl is found to follow one of three pathways: direct impulsive scattering, thermal accommodation followed by prompt desorption, and temporary trapping through HO--- HCl hydrogen bond formation.

Dynamics of HCl collisions with hydroxyl- and methyl-terminated self-assembled monolayers.

Molecular beam scattering techniques are used to explore the energy exchange and thermal accommodation efficiencies of HCl in collisions with long-chain OH- and CH(3)-terminated self-assembled monolayers (SAMs) on gold. Upon colliding with the nonpolar methyl-terminated SAM, HCl (E(i) = 85 kJ/mol) is found to transfer the majority, 83%, of its translational energy to the surface. The extensive energy loss for HCl helps to bring the molecules into thermal equilibrium with the monolayer.