Superfluid helium droplets are doped with potassium atoms forming a complex where the metal atom is weakly bound to the surface of the cluster. The dynamics of this system upon electronic excitation of the metal atom is probed by means of femtosecond pump-probe spectroscopy. Different effects are observed depending on the alignment of the potassium's upper p-orbital. A transition into the II-type state leads to ultrafast quantum interferences. Owing to the broadening of the potassium's absorption in the helium enviroment, the lifetime extremely shortens (≈ 1.5 ps) compared to the excited free potassium atom. Exciting a ∑-type state, the strong repulsive interaction with the helium surface comes into play. The corresponding response time of the helium environment is measured.
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