Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 35: Spectroscopy in He Droplets

MO 35.6: Talk

Friday, March 18, 2011, 11:45–12:00, MER 02

Line broadening in electronic spectra of molecules doped into superfluid helium nanodroplets — •Ricarda Riechers¹, Dominik Pentlhner², and Alkwin Slenczka¹ — ¹Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93053 Regensburg, Germany — ²Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark

Line broadening was found in the electronic spectra of several organic compounds doped into superfluid helium droplets. The investigation of photochemical processes such as proton transfer by means of electronic spectroscopy showed also line broadening. This observation is counterintuitive to what is expected from helium droplets, a host system at a temperature of 0.37 K. It is in contrast to sharp transitions in the corresponding gas phase spectra. Evidently, the line broadening is due to the interaction between dopant and helium environment. Electronic spectra of phthalocyanine derivatives, anthracene derivatives [1], some pyomethene dye molecules and 3-hydroxyflavone [2] (as a photochemical system), allow to deduce a mechanism explaining all the observed variations of line broadening including earlier reports on aniline [3] and adenine derivatives [4]. According to this mechanism electronic spectroscopy in superfluid helium droplets appears to be highly sensitive to changes in the electronic density distribution.

[1] D. Pentlehner et al., J. Chem. Phys. 133, 114505 (2010). [2] R. Lehnig et al., J. Chem. Phys. 131, 194307 (2009). [3] E. Loginov et al., Phys. Rev. Lett. 95, 163401 (2005). [4] S. Smolarek et al., Phys. Chem. Chem. Phys. 12, 15600 (2010).