Quantum dynamics of proton migration in H2O dications: formation of H2+ on ultrafast timescales

TL;DR

This study investigates ultrafast proton migration in water dications induced by intense laser pulses, revealing formation of vibrationally excited H2+ ions through wavepacket dynamics on an ab initio potential energy surface.

Contribution

It combines experimental ion yield measurements with theoretical wavepacket simulations to elucidate the ultrafast proton migration process in water dications.

Findings

Ion yields of ~1.5% for H2+ formation.

Proton migration occurs within 10 femtoseconds.

Vibrationally excited H2+ is produced in a specific spatial zone.

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 H2+ ion. Such unimolecular reactions occur on the potential energy surface of the H2O2+ dication that is accessed when peak laser intensities in the 1015 W cm-2 range and pulse durations as short as 9-10 fs are used; ion yields of ~1.5% 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 H2+ in a well-defined spatial zone.