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O: Fachverband Oberflächenphysik

O 22: Ultrafast Surface Dynamics

O 22.9: Vortrag

Dienstag, 17. März 2015, 12:45–13:00, MA 042

Velocity map imaging of ultrafast electron emission from fs-laser illuminated nanoscale metal tips — Alexander Bainbridge and •William Bryan — Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, UK

We have recently demonstrated velocity map imaging (VMI) of photoelectron emission from a metal nanotip illuminated with a strong field laser pulse [1]. We will present theoretical and experimental results demonstrating the simultaneous momentum resolution of electrons emitted from gas and solid targets. Above threshold ionization from krypton gas facilitates momentum calibration, and tunnelling from a metal nanotip exhibits a hemispherical momentum distribution defined by discrete photon absorption. Numerical simulations show VMI condition are maintained over a wide range of instrument configurations such that momentum focusing is independent of the emission location.

Forthcoming experiments will involve cryogenic sharpening of nanotips to a single atom, traditionally observed with field ion microscopy. As the nanotip approaches a single atom, the observed velocity map image will tend towards that of a gas phase atom, showing recollisional interference. This hybrid of real-space and momentum-space imaging will be decisive in the design of next-generation femtosecond electron diffraction and microscopy instruments.

[1] A R Bainbridge and W A Bryan, New J. Phys. 16 (2014) 103031