  Ionization of gas-phase organic molecules such as polycyclic aromatic
hydrocarbons (PAHs) requires vacuum ultraviolet photons at wavelengths shorter
than 200 nm (~6-9 eV). We present here for the first time that visible photons
- accessible through sunlight - can cause photoionization of trapped PAHs in
cryogenic water-ice, accounting for 4.4 eV less ionization energy than in the
gas phase. This finding opens up new reaction pathways involving low-energy
ionization in many environments where water and organic matter coexist. This
include the interstellar medium, molecular clouds, protoplanetary disks, and
planetary surfaces and atmospheres (including Earth).
