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Abstract. We show that the limit of the enhancement of coagulation scavenging of charged particles is 2, that is, doubled compared to the neutral case.Because the particle survival probability decreases exponentially as the coagulation sink increases, everything else being equal, the doubling of the coagulation sink can amount to a dramatic drop in survival probability – squaring the survival probability, p2, where p≤1 is the survival probability in the neutral case.Thus, it is imperative to consider this counterbalancing effect when studying ion-induced new-particle formation and ion-enhanced new-particle growth in the atmosphere. 

Organic aerosols comprise a rich mixture of compounds, many generated via nonselective radical oxidation. This produces a plethora of products, most unidentified, and mechanistic understanding has improved with instrumentation. Recent advances include recognition that some peroxy radicals undergo internal H-atom transfer reactions to produce highly oxygenated molecules and recognition that gas-phase association reactions can form higher molecular weight products capable of nucleation under atmospheric conditions. Particles also range from molecular clusters near 1 nm diameter containing a few molecules to coarse particles above 1 μm containing 1 billion or more molecules. A mixture of organics often drives growth of particles. We can describe this via detailed thermodynamics, and we can also describe the physics driving mixing between separate populations containing semi-volatile organics. Finally, fully size-resolved particle microphysics enables detailed comparisons between theory and observations in chamber experiments.