Superfluid helium droplets (He_N, N ≈ 5000) are condensed in a supersonic expansion and doped with potassium atoms. Interferometric femtosecond pump-probe spectroscopy is applied to measure the short time dynamics upon electronic excitation to the 4_p~2P_(1/2,3/2) state. To characterize the decline of the laser-induced coherence the quantum interference structure in the measured time spectra is analyzed. Aligning the excited p-orbital parallel to the surface of the droplet we find a lifetime of the observed structure ranging from 452 fs to 878 fs depending on the excitation energy.
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