Düsseldorf 2007 – wissenschaftliches Programm
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SYMC: Symposium Molecular Collisions at ultracold temperatures
SYMC 1: Molecular collisions at ultracold temperatures I
SYMC 1.3: Hauptvortrag
Montag, 19. März 2007, 15:00–15:30, 5D
Photodynamics of Atoms in and on Helium Nanodroplets — •Marcel Drabbels — Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
The photodynamics of excited silver atoms dissolved in, and sodium atoms attached to helium nanodroplets has been investigated. Embedded silver atoms are excited from the 5s 2 S 1/2 state to either the 5p 2P1/2 or 2P3/2 state. The excited species are subsequently ionized by a second photon to provide time-of-flight mass spectra, photoelectron and ZEKE spectra. The experiments indicate that the helium environment induces non-adiabatic transitions between the different electronic states before the silver atoms are being ejected from the droplets. Ion imaging experiments demonstrate that the speed distributions of ejected Ag atoms depends on the excited state and consequently are not related to the critical Landau velocity, i.e. the velocity below which no energy and momentum can be transferred from a moving object to the helium environment.
Sodium atoms attached to the surface of the droplets are electronically excited and subsequently ionized. The excitation spectrum has been recorded up to the ionization threshold and indicates that the sodium atoms desorb from the droplets independent of the electronic state excited. Photoelectron spectroscopy and ion imaging experiments indicate that the helium environment induces a fast relaxation of the excited sodium atoms before they desorb from the droplets.