Three-Body Fragmentation from Single Ionization of Water by Electron Impact: The Role of Satellite States

Ionization of water with energy transfers close to the 2a₁ inner valence orbital is accompanied by a fast electronic rearrangement driven by electron relaxation and electron-electron correlations. Quasi-degenerate single vacancy and satellites one-electron-two-vacancies excited states in outer shells are created and leave their fingerprints in the three-body fragmentation pattern. Single vacancy states have been associated with Auger decay and double ionization. Satellite excited states are here convincingly assigned to single ionization. We focus on the H⁰ + O⁺ + H⁰ fragmentation by electron impact taking advantage of the high sensitivity of the delayed extraction time-of-flight technique to uncover kinematic attributes of suprathermal O⁺ ions. It is found that the H⁰ ejections occur under a large angular rearrangement, in an approximate linear geometry, and leaving the O⁺ near at rest, with ∼50% of the O⁺ produced in water fragmentation by swift electrons presenting this feature.