Hannover 2020 – scientific programme

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MO: Fachverband Molekülphysik

MO 13: Cold Molecules (joint session MO/Q)

MO 13.4: Talk

Wednesday, March 11, 2020, 14:45–15:00, f102

Line shape investigation of the electronic origin of phthalocyanines, porphyrins and their clusters with H2O I: Helium nanodroplet studies — •Johannes Fischer, Florian Schlaghaufer, and Alkwin Slenczka — Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93053 Regensburg, Germany

Despite vanishing viscosity the spectral shape of the zero phonon line at the electronic origin of molecules embedded into superfluid helium nanodroplets does not reveal the band system of a free rotor. According to previous investigations, helium induced inhomogeneous line broadening dominates the experimentally observed optical line shape. To decipher pure molecular and helium induced contributions the line shapes of various organic compounds and their clusters with H2O were recorded by means of electronic spectroscopy as well as electronic Stark spectroscopy. In order to learn about the dopant species its spectroscopic response must be separated from the helium induced spectral features. We present electronic spectra and Stark-spectra of phthalocyanine-H2O clusters, dipolar chloroaluminiumphthalocyanine, and of chloroaluminiumphthalocyanine-H2O clusters. Thereby we observe field induced optical anisotropy and spectral changes of the line shape. A final analysis requires in addition high-level ab initio calculations for the corresponding isolated species [1]. Moreover, the helium droplet work is accompanied by corresponding investigations in the gas phase, which are subject of a follow up talk (F. Schlaghaufer).

[1] J. Fischer et al., J. Phys. Chem., 123, 10057, (2019).