Photon-gated spectral hole burning by donor-acceptor electron transfer

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Abstract
We have observed a new mechanism for photon-gated spectral hole burning, donor-acceptor electron transfer, in a material composed of a zinc-tetrabenzoporphyrin derivative (donor) with chloroform acceptors in poly(methyl methacrylate) thin films. Gated holes form when we simultaneously excite the donor 0-0 singlet absorption (630 nm) and the donor triplet–triplet absorption (350–550 nm), with the largest gating enhancement (>30) occurring for gating light near 480 nm. The gating action spectrum and the photoproduct spectrum confirm that the mechanism is electron transfer from an excited triplet of the porphyrin donor to the chloroform acceptor. This result opens up a new class of materials for photon gating that should be of interest for frequency-domain optical storage applications as well as high-resolution spectroscopy of electron transfer processes in solids.