Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 22: Femtosecond Spectroscopy IV

MO 22.1: Talk

Thursday, March 17, 2011, 14:30–14:45, TOE 317

Vibrational relaxation and decoherence of Rb₂ attached to helium nanodroplets — •Barbara Grüner¹, Martin Schlesinger², Walter T. Strunz², Frank Stienkemeier¹, and Marcel Mudrich¹ — ¹Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany — ²Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany

We study the vibrational dynamics of rubidium dimers in triplet states, which are attached to superfluid helium nanodroplets. The oscillatory dynamics can be followed with high time resolution using femtosecond pump-probe spectroscopy. The slow decrease of signal contrast can be explained by decoherence due to weak coupling to the cold helium nanodroplet. Comparison with theoretical simulations reveals that the decoherence is mainly induced by energy dissipation. The molecules lose energy towards the cold bath and thereby relax stepwise down the vibrational ladder. The relaxation rate is found to be almost constant for excitation at low vibrational levels and to rise sharply when excited to higher levels. This may be related to fast heating of the helium droplet and subsequent loss of superfluidity.