Water fragmentation induced by ion impact: Fragment-ion-energy determination at different ZP/v regimes

Abstract

This work focuses on the energy distributions of positive water ionic fragments produced by ion impact at MeV impact energies. An improved Coulomb explosion model coupled to a classical trajectory Monte Carlo simulation is used to provide energy centroids of the fragments for the dissociation channels resulting from the removal of two to five electrons from the water molecule. This model explicitly includes the post-collisional interaction of the projectile with the resulting ionic fragments affecting their kinetic energy release spectra especially at low impact energies. Theoretical data are benchmarked against recent data collected for 220 keV Xe22+ + H2O collisions which corresponds to a large ZP/v collision parameter. To extend our tests to the low ZP/v regime, fragment species as a function of emission energy and time-of-flight were recorded in 3 MeV Li3+ collisions by using an electrostatic spectrometer and a time-of-flight mass spectrometer, respectively. Present experimental data reveals the existence of multiple-ionization processes leading to charge state up to 4+.