Erlangen 2018 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 14: Atomic Clusters III (joint session A/MO)

MO 14.4: Vortrag

Mittwoch, 7. März 2018, 14:45–15:00, K 2.016

Size-dependent angular anisotropy in ion and electron emission of free NaCl nanoparticles excited by intense femtosecond laser pulses studied by Velocity Map Imaging spectroscopy — •Felix Gerke, Lucia Merkel, Egill Antonsson, and Eckart Rühl — Physikalische Chemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin

We present results regarding the angular distribution of ions and electrons emitted from NaCl nanoparticles (d = 100-500 nm) during photoionization by intense femtosecond laser pulses obtained from Velocity Map Imaging (VMI) spectroscopy. The beam of a pulsed Ti:Sapphire laser (λ = 800 nm, E = 1.55 eV) is crossed in vacuum with a beam of free NaCl nanoparticles, that is focused by an aerodynamic lens, leading to ionization of the nanoparticles. Electrons and ions emitted from the nanoparticles are recorded by a VMI spectrometer. A size-dependent asymmetry in the electron and ion emission with respect to the propagation direction of the laser beam is observed. Here, more electron and ion emission is observed in the propagation direction of the laser pulses than in opposite direction. A comparison of electron and ion emission from nanoparticles of different size reveals the angular anisotropy, which is increasing with nanoparticle size. Furthermore, a comparison to model calculations simulating the internal electric field of the nanoparticles by means of the discrete dipole approximation is used to attribute the experimentally observed angular anisotropy to size-dependent non-isotropic internal electric fields in the nanoparticles.