Proton ejection from molecular hydride clusters exposed to strong x-ray pulses.

Clusters consisting of small molecules containing hydrogen do eject fast protons when illuminated by short x-ray pulses. A suitable overall charging of the cluster controlled by the x-ray intensity induces electron migration from the surface to the bulk leading to efficient segregation of the protons and to a globally hindered explosion of the heavy atoms even outside the screened volume. We investigate this peculiar effect systematically along the isoelectronic sequence of methane over ammonia and water to the atomic limit of neon as a reference. In contrast to core-shell systems where the outer shell is sacrificed to reduce radiation damage, the intricate proton dynamics of hydride clusters allows one to keep the entire backbone of heavy atoms intact.