SAMOP 2023 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Electronic Spectroscopy

MO 5.7: Talk

Tuesday, March 7, 2023, 12:30–12:45, F142

Measuring fluorescence-detected two-quantum photon echoes using cogwheel phase cycling — •Ajay Jayachandran, Stefan Müller, and Tobias Brixner — Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

We describe two-quantum photon echo spectroscopy, a new technique that enables one the selective characterization of doubly excited states. This technique is analogous to the popular ‘photon echo’ experiment [1], which encodes the dynamic information associated with singly excited states.

We transfer the core principle, i.e., a rephasing contribution that removes the effect of inhomogeneous broadening, to doubly excited states, and we extract the signal experimentally using cogwheel phase cycling of three-pulse sequences and fluorescence detection. We verify the applicability of cogwheel phase cycling, which has proven useful in two-dimensional nuclear magnetic resonance spectroscopy to reduce overall measurement time in comparison to nested phase cycling [2], by extracting the two-quantum photon echo without any signal aliasing.

We study how exciton–exciton annihilation of squaraine molecular aggregates of varying chain length [3] can be quantified by accessing the homogenous linewidth of the biexciton state which is obtained from the two-quantum photon echo.

[1] S. Asaka et al., Phys. Rev. A. 29, 2286-2289 (1984).

[2] M. H. Levitt et al., J. Magn. Reson. 155, 300-306 (2002).

[3] P. Malý et al., Chem. Sci. 11, 456-466 (2020).