Periodic Reporting for period 1 - PROIRICE (Proton-Irradiated Ice: Dynamics and Chemistry from First Principles)
Reporting period: 2017-10-01 to 2019-09-30
The precise objectives of the project are:
- To obtain a theoretically accurate description, at the level of the dynamics of electrons and nuclei, of the process of proton irradiation on pure water ice and its effects on the ice structure, with particular emphasis on the influence of the proton energy and trajectory on the effects of proton irradiation.
- To obtain an equally accurate description of the chemical reactions triggered by proton irradiation of water ice, be it pure or mixed (i.e. containing simple molecules such as CO or NH3)
In addition, the previous simulations provide information about what is the energetic distribution of the electronic excitations in the system, which informs us about the likelihood of an ionization event occurring, and about which electrons are most likely to be “ejected” of the system, i.e. which water molecules are most likely to get ionized. With this starting information, we have been able to model the dynamics of an ice system where one or two water molecules have been ionized, successfully observing the splitting of a water molecule into an OH· radical and an H+ that migrates through the water network in the first case, and when two neighboring waters are ionized, observing the splitting of both of them and the subsequent reaction of the two OH· radicals to form a molecule of hydrogen peroxide. These results open the door to efficient and accurate simulations of post-ionization processes of chemical systems, which can again be useful for a very wide number of scientific/technological problems, from radiation therapy to materials processing.
Finally, we carried out simulations of the proton irradiation of water ice containing molecules such as CO or NH3. These simulations again provide information about the energy absorbed by the system due to the irradiation event, and about what would be the most probable ionized states that would be obtained after the irradiation.