Subfemtosecond<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>-Shell Excitation with a Few-Cycle Infrared Laser Field

Abstract

Subfemtosecond bursts of extreme ultraviolet radiation, facilitated by a process known as high-order harmonic generation, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe ultrafast dynamics in the microcosms of atoms, molecules, and solids. These ultrashort pulses are always, and as a by-product of the way they are generated, accompanied by laser-induced recollisions of electrons with their parent ions. By using a few-cycle infrared (λ(0)=2.1 μm) driving laser, we were able to directly excite high-energy (∼870 eV) inner-shell electrons through laser-induced electron recollision, opening the door to time-resolved studies of core-level and concomitant multielectron dynamics.