Inelastic electron injection in a water chain

Valerio Rizzi,Jorge J Kohanoff,Tchavdar N Todorov

doi:10.1038/srep45410

Abstract

Irradiation of biological matter triggers a cascade of secondary particles that interact with their surroundings, resulting in damage. Low-energy electrons are one of the main secondary species and electron-phonon interaction plays a fundamental role in their dynamics. We have developed a method to capture the electron-phonon inelastic energy exchange in real time and have used it to inject electrons into a simple system that models a biological environment, a water chain. We simulated both an incoming electron pulse and a steady stream of electrons and found that electrons with energies just outside bands of excited molecular states can enter the chain through phonon emission or absorption. Furthermore, this phonon-assisted dynamical behaviour shows great sensitivity to the vibrational temperature, highlighting a crucial controlling factor for the injection and propagation of electrons in water.

Highlights

Irradiation of biological matter triggers a cascade of secondary particles that interact with their surroundings, resulting in damage
DFT calculations of the excited states of a corresponding system show the formation of a band analogous to the first conduction band (FCB) and, above it, a continuum of states which is not captured in our simple TB model because of the reduced number of basis functions for water empty states
We have seen that electron-phonon interaction provides a key mechanism by which excited electrons can be generated in water, as inelastic electron-phonon injection is a critical process in granting incoming electrons access to the water excited states

Summary

Introduction

Irradiation of biological matter triggers a cascade of secondary particles that interact with their surroundings, resulting in damage. In this paper we combine ECEID with electronic Open Boundaries (OB)[10] to simulate in real time the injection of LEEs and their inelastic dynamical interaction with phonons. For incident pulses above the upper band edge, 〈E〉> 6.5 eV, electrons have to emit a phonon to enter the water FCB, so one expects a ΔN> 0.

Results

Conclusion