Background-free measurement of exciton-exciton annihilation by two-quantum fluorescence-detected pump-probe spectroscopy
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| Format: | Preprint |
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2026
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| _version_ | 1866914558191337472 |
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| author | Jayachandran, Ajay Mueller, Stefan Lambert, Christoph Brixner, Tobias |
| author_facet | Jayachandran, Ajay Mueller, Stefan Lambert, Christoph Brixner, Tobias |
| contents | We introduce two-quantum (2Q) fluorescence-detected pump-probe (F-PP) spectroscopy as a tool to probe ultrafast multiparticle interactions in many-body systems. We describe a pulse-shaper-based fully collinear setup utilizing phase cycling to capture the 2Q F-PP signal simultaneously with the one-quantum (1Q) F-PP signal. Thus, we investigate the dynamics of energy transfer and diffusion-limited annihilation. We apply a data post-processing strategy to isolate excited-state dynamics from spurious background. The technique is applied to a squaraine heterodimer and a squaraine copolymer to demonstrate the removal of so-called incoherent mixing that generally plagues action-detected nonlinear spectroscopy on multichromophoric systems. Specifically, we show that this approach is not only applicable to 1Q but also to 2Q F-PP signals, eliminating incoherent mixing contributions as well as other "parasitic" signals that result from pulse-overlap ambiguities. As a result, we retrieve background-free spectral and dynamical information of doubly excited electronic states. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_11984 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Background-free measurement of exciton-exciton annihilation by two-quantum fluorescence-detected pump-probe spectroscopy Jayachandran, Ajay Mueller, Stefan Lambert, Christoph Brixner, Tobias Chemical Physics Optics We introduce two-quantum (2Q) fluorescence-detected pump-probe (F-PP) spectroscopy as a tool to probe ultrafast multiparticle interactions in many-body systems. We describe a pulse-shaper-based fully collinear setup utilizing phase cycling to capture the 2Q F-PP signal simultaneously with the one-quantum (1Q) F-PP signal. Thus, we investigate the dynamics of energy transfer and diffusion-limited annihilation. We apply a data post-processing strategy to isolate excited-state dynamics from spurious background. The technique is applied to a squaraine heterodimer and a squaraine copolymer to demonstrate the removal of so-called incoherent mixing that generally plagues action-detected nonlinear spectroscopy on multichromophoric systems. Specifically, we show that this approach is not only applicable to 1Q but also to 2Q F-PP signals, eliminating incoherent mixing contributions as well as other "parasitic" signals that result from pulse-overlap ambiguities. As a result, we retrieve background-free spectral and dynamical information of doubly excited electronic states. |
| title | Background-free measurement of exciton-exciton annihilation by two-quantum fluorescence-detected pump-probe spectroscopy |
| topic | Chemical Physics Optics |
| url | https://arxiv.org/abs/2605.11984 |