Isolated 170 as Pulse Generation in the XUV

Abstract

Macroscopic properties of matter constitute the manifestation of ultrafast phenomena evolving on a microscopic scale in atoms, molecules, and solids. Insight into these phenomena calls for experimental techniques endowed with temporal resolution commensurable with their characteristic time scale. This time scale of microscopic phenomena is predictable via the laws of quantum mechanics. For example, in a molecule, the sub-meV spacing of the rotational energy levels and the sub-eV spacing for the vibrational ones correspond to picosecond (1 ps = 10−12 s) and femtosecond (1 fs = 10−15 s) time scales, respectively. Phenomena evolving on a femtosecond time scale have been resolved in real time owing to the development of femtosecond laser pulses which marked the era of femtoscience [1]. However, the resolution that these pulses provide is inadequate for tracking and controlling the motion of electrons in atoms and molecules. Based on similar arguments as above, an electronic wave packet formed by the coherent superposition of lower electronic states of an atom or a molecule (typically spaced in energy by few eV) will evolve on an attosecond time scale (1 as = 10−18 s). In many cases the evolution of electron wave packets results in electronic charge redistribution ∗corresponding author; e-mail: elgo@mpq.mpg.de