Femtosecond Core-Level Charge Transfer

TL;DR

This paper demonstrates that ultrafast, few-femtosecond core-level charge transfer can occur in molecules following core-excitation, driven by non-adiabatic electronic coherences, challenging the assumption that charge transfer always takes tens to hundreds of femtoseconds.

Contribution

The study reveals that core-level charge transfer can happen within 5 femtoseconds, driven by non-adiabatic dynamics, showing a new ultrafast process in molecular charge transfer phenomena.

Findings

Core-hole localization occurs within 5 fs.

Core-hole delocalization happens within the Auger decay window.

Ultrafast charge transfer driven by nuclear dynamics can match electronic charge migration timescales.

Abstract

Charge transfer is a fundamental phenomenon in biology and chemistry, and involves the movement of charge through a system driven by nuclear dynamics. Because of the involvement of nuclear motion, it is generally assumed that charge transfer will occur on a time-scale of some few tens-to-hundreds of femtoseconds. Using the example of ethylene excited to its $1s\pi^{*}$ manifold, we demonstrate that ultrafast, few-femtosecond core-level charge transfer may occur following core-excitation, driven by the formation of electronic coherences by non-adiabatic dynamics. Here, transfer of core-electron density from one side of the molecule to the other is driven by a breakdown of the Born-Oppenheimer approximation, and results in core-hole localisation occuring within 5 fs, followed by core-hole delocalisation, all within the Auger decay window. These results serve to demonstrate that ultra-fast core-level charge transfer driven by nuclear dynamics may occur on the same timescale as purely electronic, i.e., charge migration, dynamics following core-excitation.