Multi-ion emission from large and massive keV cluster impacts

We report the first measurements of the distributions of the number of molecular ions emitted per gold cluster impact. Experiments were performed in the event-by-event bombardment/emission mode. Targets of phenylalanine were bombarded with 28.6 keV Au9+ and 134.6 keV Au4004+ projectiles. The secondary ions were identified with a linear time-of-flight mass spectrometer equipped with an 8-anode detector, thus allowing to record the co-emission of up to 8 phenylalanine ions. We describe how the experimentally measured molecular ion distribution is related to the initial distributions of ionized and neutral molecules.