Water fragmentation by bare and dressed light ions with MeV energies

WOLFF, W.; SCHUCH, R.; LUNA, H.; CARIATORE, N. D.; OTRANTO, S.; TURCO, F.; FREGENAL, D.; BERNARDI, G.; SUARÉZ, S.

Kielce

Conferencia; 18th International Conference on the Physics of Highly Charged Ions; 2016

The report presents data on the ionization and fragmentation of water induced by H^+, Li^{0-3+}, and C^{1,2+} impact in the intermediate energy range of 1.6 to 5.8 MeV, with focus on the energy and time-of-flight distributions of water ionic fragments (fig.1). Two experimental approaches based on an electrostatic spectrometer were applied to investigate the fragmentation channels, in one case fragment-ion energy distributions were recorded, while in the second setup, the Pelletron accelerator was operated in pulse mode and the spectrometer acted as a time of flight spectrometer. The experimental findings were compared to a model based on Classical Trajectory Monte Carlo calculations which were married to a coulomb Explosion Model.The combined experimental and theoretical study reveals isotropic production of charged ions and show, besides the most abundant H^+ ions, highly-charged O^{q+} fragments with charges up to 5+. From the ion energy distribution and time of flight spectra relative yields of the dissociation resulting from multiple-ionization were extracted as function of neutral to bare projectiles, for several projectile energies, and fragment-ions energies, probing distinct scopes of the water fragmentation. The calculations indicate that close collisions between the projectile and the target atoms lead to multiple ionization and can be related to the O^{q+} population. Although there are studies concerning the influence of the velocity and charge state of the projectile on the dissociation of water [1], a detailed knowledge of features of the dissociation pattern leading to the formation of multiply charged ion-pairs in the intermediate energy range remains scarce.