Photo-initiated ground state chemistry: How important is it in the atmosphere?

Carbonyls are among the most abundant volatile organic compounds in the atmosphere. They are central to atmospheric photochemistry as absorption of near-UV radiation by the C=O chromophore can lead to photolysis. If photolysis does not occur on electronic excited states, non-radiative relaxation to the ground state will form carbonyls with extremely high internal energy. These “hot” molecules can access a range of ground state reactions. Up to nine potential ground state reactions are investigated at the B2GP-PLYP-D3/def2-TZVP level of theory for a dataset of 20 representative carbonyls. Almost all are energetically accessible under tropospheric conditions. Comparison with experiment suggests the most significant ground state dissociation pathways will be concerted triple fragmentation in saturated aldehydes, Norrish type III dissociation to form another carbonyl, and H2-loss involving the formyl H atom in aldehydes. Tautomerisation, leading to more reactive unsaturated species, is also predicted to be energetically accessible and is likely to be important when there is no low-energy ground state dissociation pathway, for example in α,β-unsaturated carbonyls and some ketones. The concerted triple fragmentation and H2-loss pathways have immediate atmospheric implication to global H2 production and tautomerisaton has implication to the atmospheric production of organic acids.

Theoretical study of the Cl(2P) + SiH4 reaction: Global potential energy surface and product pair-correlated distributions. Comparison with experiment.

For the theoretical study of the title reaction, an analytical full-dimensional potential energy surface named PES-2021 was developed for the first time, by fitting high-level explicitly-correlated ab initio data. This...

CONRAD – a code for nuclear data modeling and evaluation

The CONRAD code is an object-oriented software tool developed at CEA since 2005. It aims at providing nuclear reaction model calculations, data assimilation procedures based on Bayesian inference and a proper framework to treat all uncertainties involved in the nuclear data evaluation process: experimental uncertainties (statistical and systematic) as well as model parameter uncertainties. This paper will present the status of CONRAD-V1 developments concerning the theoretical and evaluation aspects. Each development is illustrated with examples and calculations were validated by comparison with existing codes (SAMMY, REFIT, ECIS, TALYS) or by comparison with experiment. At the end of this paper, a general perspective for CONRAD (concerning the evaluation and theoretical modules) and actual developments will be presented.