TY - JOUR
T1 - Distinguishing Mechanisms for Reactive Uptake at Liquid Surfaces via Angular Distributions of Inelastically Scattered Molecules
AU - Roman, Maksymilian J.
AU - Knight, Adam G.
AU - Moon, Daniel R.
AU - Lane, Paul D.
AU - Costen, Matthew L.
AU - McKendrick, Kenneth G.
N1 - Publisher Copyright:
© 2024 The Authors. Published by American Chemical Society.
PY - 2024/7/4
Y1 - 2024/7/4
N2 - Angular distributions of OH inelastically scattered from the surfaces of the reactive hydrocarbon liquids squalane (fully saturated) and squalene (partially unsaturated) have been measured. A pulsed, rotationally cold molecular beam (Ei = 35 kJ mol-1) of OH was scattered from refreshed liquid surfaces in a vacuum. Spatially and temporally resolved OH number densities were measured by pulsed, planar laser-induced fluorescence. Results are compared with those for the inert liquid perfluoropolyether. The clearly asymmetric distributions for 45° incidence add to the weight of evidence for predominantly impulsive scattering from all three liquids. However, we propose that significant differences in their shapes may be diagnostic of contrasting reaction mechanisms. Direct, near-specular trajectories survive preferentially on squalene, consistent with an addition mechanism removing those at more backward angles. This trend is reversed for squalane, as expected for direct abstraction. The results reinforce the need to consider the effects of composition-dependent contributions from different reaction mechanisms in the modeling of OH-aging of atmospheric aerosol particles.
AB - Angular distributions of OH inelastically scattered from the surfaces of the reactive hydrocarbon liquids squalane (fully saturated) and squalene (partially unsaturated) have been measured. A pulsed, rotationally cold molecular beam (Ei = 35 kJ mol-1) of OH was scattered from refreshed liquid surfaces in a vacuum. Spatially and temporally resolved OH number densities were measured by pulsed, planar laser-induced fluorescence. Results are compared with those for the inert liquid perfluoropolyether. The clearly asymmetric distributions for 45° incidence add to the weight of evidence for predominantly impulsive scattering from all three liquids. However, we propose that significant differences in their shapes may be diagnostic of contrasting reaction mechanisms. Direct, near-specular trajectories survive preferentially on squalene, consistent with an addition mechanism removing those at more backward angles. This trend is reversed for squalane, as expected for direct abstraction. The results reinforce the need to consider the effects of composition-dependent contributions from different reaction mechanisms in the modeling of OH-aging of atmospheric aerosol particles.
UR - http://www.scopus.com/inward/record.url?scp=85196828228&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.4c02917
DO - 10.1021/acs.jpca.4c02917
M3 - Article
C2 - 38915192
AN - SCOPUS:85196828228
SN - 1089-5639
VL - 128
SP - 5166
EP - 5174
JO - The Journal of Physical Chemistry A
JF - The Journal of Physical Chemistry A
IS - 26
ER -