Heidelberg 2015 – wissenschaftliches Programm
A 25.6: Vortrag
Mittwoch, 25. März 2015, 16:00–16:15, PH/SR106
Angular distribution of electron and photon emission from isolated SiO2 nanopartices excited by femtosecond laser pulses — •Egill Antonsson, Ina Halfpap, Christopher Raschpichler, Valerie Mondes, Jürgen Plenge, Burkhard Langer, and Eckart Rühl — Physical Chemistry, Freie Universität Berlin, Takustr. 3, 14195 Berlin
We excite isolated spherical SiO2 nanoparticles (diameter: 90 nm, size distribution: 8%) with intense femtosecond laser pulses (λ=800 nm, τ=80 fs, Intensity: 1-3·1013 W/cm2) and study the angular distribution of emitted electrons and UV photons (hν>8 eV). The nanoparticles are prepared in an aerodynamically focused beam which propagates into a high vacuum system where excitation and photoionization occurs. This ensures that fresh sample is available to each laser pulse and rules out effects due to particle-particle interactions, sample charging, and radiation damage. For electron emission, a distinct angular dependence with respect to the polarization vector of the laser pulses is observed, which varies for different photoelectron energies. High-energy photoelectrons are found to be emitted preferentially parallel to the polarization vector of the exciting laser photons, which is discussed in terms of an elastic scattering of continuum electrons at or near the surface of the nanoparticles. For low-energy photoelectrons, on the other hand, the angular dependence is quenched due to multiple inelastic scattering events of the photoelectrons in the nanoparticles which smears out angular effects.