Limitations of high-intensity soft X-ray laser fields for the characterisation of water chemistry: Coulomb explosion of the octamer water cluster

Abstract

In this work, the Coulomb explosion of the octamer water cluster has been studied employing a theoretical approach. Instead of the usual methodology that makes use of classical molecular dynamics, time-dependent density functional theory has been applied to tackle the problem. This method explicitly accounts for the laser field and thus does not impose any constraint on the interaction between the laser pulse and the cluster. We focus on the effects of energetic changes in the system under high-intensity soft X-ray laser pulses. The motions of the ions and their velocities during this process show significant differences for the three applied laser intensities (10¹⁴, 10¹⁵ and 10¹⁶ W cm⁻²). Very strong soft X-ray free electron laser (FEL) pulses must be short to allow for investigations of ultra-fast wet chemistry, according to the principle of collect and destroy.