- Rate constants for gas-phase reactions: Rate constants associated to gas‐phase reactions are typical data products obtained from simulation chamber experiments. They are extremely useful for modelers to calculate rates of chemical reactions and to identify major pathways. They are used in 0D models in which a very detailed chemistry is usually described as well as in 3D models which use simplified chemical schemes for application in air quality forecasts, for example. They are also useful for the interpretation of atmospheric observations as they allow evaluating the formation rates and the atmospheric lifetimes of trace species in the gas‐phase.
- Rate constants for condensed-phase reactions: Similarly to gas‐phase rate constants, rate constants of condensed‐phase reactions are extremely useful for modelers to calculate rates of chemical reactions and to identify major pathways. They are used in 0D models in which a very detailed chemistry is usually described as well as in 3D models (chemical‐transport models) which use simplified chemical schemes. They are also useful for the interpretation of atmospheric observations as it allows evaluating the formation rates and the atmospheric lifetimes of trace species in condensed phases.
- Secondary Organic Aerosol (SOA) yields: Defined by the aerosol mass produced from a specific chemical process under well‐defined aerosol load conditions, secondary organic aerosol yields are typical outputs from chamber measurements. When produced under realistic atmospheric conditions, they are extremely useful for modelers who can associate an aerosol production in a lumped processed. They are also useful on the field to link emissions molecular distributions to secondary aerosol production.
- Photolysis frequencies: Photolysis frequencies are very useful to calculate the photolysis rates of atmospheric trace species in 0D and 3D models. These data are available for a limited number of “simple”compounds and additional data obtained for more complex molecules, in particular for multifunctional species, are absolutely necessary.
- Quantum yields: The quantum yield represents the probability that a molecule photo‐dissociates following a given pathway once it has absorbed a photon. Combined with the cross section and the actinic flux, it allows calculating the photolysis frequency of the molecule for any given condition of sunlight. These data are extremely useful to calculate the photolysis rates of trace species in 0D and 3D models as well as for the interpretation of atmospheric observations. Similarly to photolysis frequencies, these data are available for only a limited number of “simple” compounds and additional data obtained for more complex molecules, in particular for multifunctional species, are absolutely necessary.
- Vapor pressures & Henry's constants: Vapor pressure and Henry’s constant are key parameters to determine the partition of semi‐volatile / soluble compounds between gas phase and aerosol / aqueous phase respectively. They are key parameters both for modelers and for field campaign data analysis.
- Optical properties: The aerosol mass extinction coefficients (MEC) and complex refractive index (CRI) are the physical parameters expressing the capability of atmospheric aerosols to absorb and scatter radiation, henceforth their driving role in amplifying or mitigating climate change by greenhouse gases. MEC represents the efficiency of extinction (sum of scattering and absorption) by unit mass, while the CRI relates the properties of matter, and specifically the composition, to light absorption and scattering. End‐users of these products are modelers developing state‐of the art regional and global climate models for present‐day and future‐climate simulations, as well as scientists developing advanced products for remote sensing. Optical properties of particles were highlighted as the major uncertainty in constraining the direct radiative effect by the AR5 IPCC report in 2013. Major lack of data was identified in the knowledge of light‐absorption by aerosol type, henceforth its spectral dependence across the electromagnetic spectrum. As an example, organic aerosols and mineral dust absorb mostly in the UV, whereas absorption by black carbon aerosols is spectrally‐invariant. Compositional‐related differences can be masked by differences in the typical size distribution of atmospheric aerosols, or relative humidity. These contributions are difficult to disentangle if the experimental conditions are not reported. EUROCHAMP‐2020 heard the call and provides with a compilation of MEC and CRI from controlled chamber experiments.
- Growth factors: Growth factors (GF) are charactering the affinity with water of particles. They are typically a ratio between the diameter of particle under dry condition and its diameter at a reference RH. In the lab, GF are useful parameters to follow the impact of a process on water affinity. On the field, GF are often very useful to correct measured distribution from water absorption and hence close mass balance.