Flowing Gas Experiments Reveal Mechanistic Details of Interfacial Reactions on a Molecular Level at Knudsen Flow Conditions

Knudsen flow experiments and its interpretation in terms of adsorption/desorption kinetics as well quantitative uptake on substrates interest is presented together with the description critical design parameters Flow Reactor (KFR). Hitherto focused almost exclusively phase exposing a virgin substrate to interacting gases, we now extend experiment desorption at ambient temperature. We present analytical expressions for different experimental situations adsorption (k ), d ) effusion e rate constants. The measurement k leads surface residence times (1/k obtained under same conditions that results determination Langmuir equilibrium constant K L = /k . emphasize interaction semivolatile organic probe gases small polar molecules amorphous carbon mineral dust materials temperatures. latter molecular characterization scheme based use up ten reactive gases. After saturation each gas this reactivity map interface. Several examples are used underline broad applicability technique such silver/air (Ag) interface TiO 2 towards CO CH 3 OH. Following several types model incorporating structural elements agreement titration proposed. For instance, an time weakly basic strongly reducing composed pyrones hydroquinones whose simultaneous occurrence stable free radicals may play role atmospheric chemistry (EPFR). question raised what makes hydrophobic functional groups when H O(D O), HCl, NO NH Multidiagnostic studies heterogeneous reactions enabled using stirred-flow reactors (SRF) logical extension KFR approach thus relaxing requirements. Previous work SRF low-temperature O ices highlighted be exoplanetary space sciences community.