Mainz 2026 – scientific programme

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MO: Fachverband Molekülphysik

MO 32: Molecular Spectroscopy III

MO 32.4: Talk

Friday, March 6, 2026, 12:00–12:15, P 204

Helium cluster-isolation spectroscopy of quinacridone — •Aleksandr Demianenko, Kaleb Strahringer, Sebastian Hartweg, and Frank Stienkemeier — Institute of Physics, University of Freiburg, Germany

Organic chromophores are essential components of organic solar cells, field-effect transistors, light-emitting diodes, and supramolecular organic semiconductors. Their electronic and vibrational energy levels play a central role in determining collective molecular behaviors, including charge transport, exciton motion, and self-assembly.

In this talk, I will present helium cluster isolation spectroscopy to study the chromophore quinacridone. Although mostly known as an organic dye, quinacridone also shows highly interesting properties in its aggregation. Since it is a prochiral molecule it can be seen as a chiral object when attached to surfaces, where it can either aggregate in homochiral linear chains or more complex heterochiral structures.

The superfluid helium environment can be seen as isotropic thus allowing the aggregation of quinacridone molecules as non-chiral objects. Additionally, the ultracold temperature of the helium nanodroplets restrict population to vibrational ground states and produces well-resolved spectra for both monomers and oligomers in a minimally perturbing ultracold matrix. By combining a wavelength-tunable nanosecond laser, we obtain high-resolution laser-induced fluorescence spectra. These are presented in comparison with spectra on surfaces and in organic solvents.

Keywords: quinacridone; helium nanodroplets; laser-induced fluorescence; organic chromophores; collective excitation