  Understanding the mechanisms of proton energy deposition in matter and
subsequent damage formation is fundamental to radiation science. Here we
exploit the picosecond (10^-12 s) resolution of laser-driven accelerators to
track ultra-fast solvation dynamics for electrons due to proton radiolysis in
liquid water (H2O). Comparing these results with modelling that assumes initial
conditions similar to those found in photolysis reveals that solvation time due
to protons is extended by > 20 ps. Supported by magneto-hydrodynamic theory
this indicates a highly dynamic phase in the immediate aftermath of the proton
interaction that is not accounted for in current models.
