Molecular Beam Scattering of Ammonia from a Dodecane Flat Liquid Jet

The evaporation and scattering of ND3 from a dodecane flat liquid jet are investigated and compared to previous molecular beam scattering studies from liquid surfaces. Evaporation is well-described by a Maxwell–Boltzmann flux distribution with a cosθ angular distribution at the liquid temperature. Scattering experiments at Ei = 28.8 kJ mol−1 over a range of deflection angles show evidence for impulsive scattering and thermal desorption. At a deflection angle of 90°, the thermal desorption fraction is 0.54, which is ~4 % higher than other molecules previously scattered from dodecane and consistent with work performed on NH3 scattering from a squalane wetted wheel. ND3 scattering from dodecane results in super-specular scattering, as seen in previous experiments on dodecane. The impulsive scattering channel is fitted to a “soft-sphere” model, yielding an effective surface mass of 55 amu and an internal excitation of 5.08 kJ mol−1. Overall, impulsively scattered ND3 behaves similarly to other small molecules scattered from dodecane.