Characterizing divergent spin-orbit coupling effects on ultrafast nonradiative decay in transition-metal compounds

Carbery William P,Turner Daniel B,G Cerullo,F Kärtner,R Li,M Khalil,J Ogilvie

doi:10.1051/epjconf/201920505018

Abstract

Two-dimensional electronic spectroscopy reveals divergent, spin-orbit coupling mediated, electronic relaxation dynamics in iridium(IV) hexa-bromide ([IrB6]2-) and the ruthenium(II)-based DSSC dye N719.

Highlights

Conventional descriptions of excited state relaxation involve three decay pathways locked in a rigid temporal hierarchy
The ultrafast dynamics of [IrBr6]2- are best explained as interactions between spin-orbit coupled, adiabatic potential energy surfaces resulting in nonradiative decay of all LMCT transitions into the lowest excited state [13]
The observation of persistent vibrational coherence during this LMCT energy relaxation suggested conical intersection mediated nonradiative decay. This necessitated expanding the conical intersection definition to include a crossing between states of the same total angular momentum rather than merely the same spinmultiplicity [14]. This more general definition of a conical intersection helps to understand other, unusual aspects of spin-orbit coupled systems, including the observation of ultrafast intersystem crossing among the LMCT bands of [IrBr6]2, but not between its lowest-lying excited state and ground state

Summary

Introduction

Conventional descriptions of excited state relaxation involve three decay pathways locked in a rigid temporal hierarchy. Internal conversion mediated by conical intersections is considered ubiquitous, intersystem crossing is still usually considered slower than other competing relaxation pathways. Much like the early work on internal conversion and conical intersections, recent experiments on intersystem crossing suggest that transitions between two potential energy surfaces of differing spin multiplicity are highly nonadiabatic [9].

Results

Conclusion