Auger electron–ion coincidence studies to probe molecular dynamics

Abstract

Electron analysis combined with ion mass spectrometry is shown to be a unique tool to understand fragmentation dynamics of core-excited molecules. This article describes in detail a new setup devoted to energy and angle correlations measurements between the emitted particles resulting from inner-shell ionization or excitation. The data collection system is based on a pair of position sensitive detectors mounted behind a double toroidal electron analyzer and a short time-of-flight ion spectrometer. Because all relevant information results in time measurements, a natural synchronization in the events recording is obtained. The optimized geometry for the ion extraction allows spatial focusing for the ion trajectories by means of inhomogeneous extraction fields while preserving the time focusing. The N 2 molecule has been used for full characterization of the setup whereas the CO 2 molecule illustrates the role of the intermediate resonant state in controlling the final dissociation pattern. The bending mode excitation is shown to emphasize the O + production, and the ion kinetic energy distribution is rationalized through an impulsive model.