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Photon energy upconversion in porphyrins: one-photon hot-band absorption versus two-photon absorption |
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| Authors: | M. Drobizhev A. Karotki M. Kruk A. Krivokapic H. L. Anderson A. Rebane |
| Affiliation: | a Department of Physics, Montana State University, Bozeman, MT 59717-3840, USA b Dyson Perrins Laboratory, Chemistry Department, University of Oxford, South Parks Road, Oxford OX1 3QY, UK |
| Abstract: | We study the porphyrin S1→S0 fluorescence and the photosensitized singlet oxygen 1Δg→3Σg phosphorescence, both originating from absorption of photons with energy less than the porphyrin S0→S1 transition energy. By measuring the excitation intensity dependence of fluorescence at lowered sample temperatures, we are able to discriminate between two parallel processes of one-photon hot-band absorption (HBA) and simultaneous two-photon absorption (TPA). When the HBA and TPA contributions are comparable in magnitude, we use this new method to determine absolute TPA cross-section. We also demonstrate for the first time a singlet oxygen photosensitization via HBA in porphyrin. |
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