Quantum dynamics of proton migration in H 2O dications: H 2+ formation on ultrafast timescales

Abstract

Irradiation of isolated water molecules by few-cycle pulses of intense infrared laser light can give rise to ultrafast rearrangement resulting in formation of the H 2 ion. Such unimolecular reactions occur on the potential energy surface of the H 2O 2 dication that is accessed when peak laser intensities in the 10 15 W cm -2 range and pulse durations as short as 9-10 fs are used; ion yields of ∼1.5 relative to the H 2O ion are measured. We also study such reactions by means of time-dependent wavepacket dynamics on an ab initio potential energy surface of the dication and show that a proton, generated from O-H bond rupture, migrates towards the H-atom, and forms vibrationally excited H 2 in a well-defined spatial zone. © 2012 American Institute of Physics.