Cooperative energy transfer and photon absorption

Davıd L. Andrews, Philip Allcock

W. Stręk

M. Altarelli, David L. Dexter

A discussion is given of the probability of absorbing a photon while simultaneously transferring electronic excitation energy from an already excited impurity. Estimates are given for several types of systems. A comparison is made with the probability for two-photon absorption (which is much smaller) and cooperative transfer processes. Several possible experiments are suggested.

Davıd L. Andrews, Nick P. Blake

In this paper it is demonstrated how the phenomena of cooperative Raman scattering and cooperative two-photon absorption may be described in a unified manner, through canonically transforming the system Hamiltonian. The unique features associated with the virtual photon coupling between centres are discussed. In particular it is illustrated how in the near-zone, close proximity leads to two-body two-photon events involving interaction-induced dipoles. In the far-zone, it is shown how the coupling between molecules may be understood in terms of a radiative dipole effect. Attention is focused upon the behaviour of this coupling for distributive and cooperative mechanisms in fluids, and the relative importance of each process discussed, particularly with regard to their very different range dependences. A detailed analysis of the coupling reveals that in two-photon absorption the distributive mechanism dominates, whilst in Raman scattering cooperative energy transfer is favoured. Finally recent progress in the field of synergism is reviewed along with the characteristics associated with synergism in Raman scattering and two-photon absorption.

H. H. Jen

Vincent R. M. Benning, Nils van de Mortel, Midas Waakop Reijers +4 more

High Resolution Image Download MS PowerPoint Slide Spectral conversion of sunlight can enhance solar cell efficiencies by shifting short-wavelength photons to longer wavelengths, where the photovoltaic response is stronger. This can be realized with near 100% energy efficiency by materials capable of quantum cutting . These emit two longer-wavelength photons, following the absorption of one shorter-wavelength photon. Although various quantum-cutting materials have been reported, follow-up research has often disproved initial claims. Here, we demonstrate that photon correlation analysis is a universal strategy to unambiguously identify quantum cutting. We investigate two materials, YPO 4 codoped with Tb 3+ and Yb 3+ and yttrium aluminum garnet (YAG) codoped with Ce 3+ and Yb 3+ . Both are reported to perform quantum cutting via blue light absorption followed by cooperative energy transfer to near-infrared-emitting Yb 3+, but some studies have cast doubts for YAG:Ce 3+,Yb 3+ . Our correlation analysis demonstrates bunched emission for YPO 4:Tb 3+,Yb 3+, confirming quantum cutting. In contrast, YAG:Ce 3+,Yb 3+ shows Poissonian emission statistics, disproving its quantum-cutting capability, despite previous claims.