Modeling the radiolysis in H2O : HCOOH ice: connecting laboratory experiments with astronomical measurements.

We present a computational study of radiolytic chemistry and desorption dynamics in astrophysical ice composed of H2O : HCOOH (1 : 1), irradiated with Ni11+ ions at 46 MeV and 15 K. Simulations were performed using the PROCODA model, calibrated with experimental data provided by GANIL in France in 2014, to investigate molecular evolution and desorption processes with temporal resolution. The results reveal a rapid progression towards chemical equilibrium at approximately 2000 s of irradiation, followed by the stabilization of major species such as CO, CO2, CH3OH, H2CO, OH, and HCO. The model also predicts dynamic and time-dependent desorption profiles, with transient peaks reflecting the evolution of the physicochemical environment within the ice. The simulated molecular abundances in equilibrium show some agreement with infrared observations of the protostars IRAS 2A (JWST) and W33A (ISO), validating the predictive power of the model. Furthermore, the computational methodology employed predicts several chemically viable species below the current detection thresholds, highlighting targets for future observations. These results reinforce the role of ionizing radiation in the formation of ice chemistry in protoplanetary disks and demonstrate the usefulness of PROCODA in connecting laboratory astrochemistry with astronomical spectroscopy, particularly for the interpretation of molecular signatures in cold and sheltered environments.