ime-Resolved Ultrafast Interatomic Coulombic Decay in Superexcited Sodium-Doped Helium Nanodroplets

The autoionization dynamics of super excited superfluid He nanodropletsdoped with Na atoms is studied by extreme-ultraviolet (XUV) time-resolved electronspectroscopy. Following excitation into the higher-lying droplet absorption band, the dropletrelaxes into the lowest metastable atomic 1s2s1,3Sstates from which interatomic Coulombicdecay (ICD) takes place either between two excited He atoms or between an excited He atomand a Na atom attached to the droplet surface. Four main ICD channels are identified, andtheir decay times are determined by varying the delay between the XUV pulse and a UV pulsethat ionizes the initial excited state and thereby quenches ICD. The decay times for thedifferent channels all fall in the range of similar to 1 ps, indicating that the ICD dynamics are mainlydetermined by the droplet environment. A periodic modulation of the transient ICD signals istentatively attributed to the oscillation of the bubble forming around the localized Heexcitation