  We investigate, from a theoretical perspective, photo-emission of electrons
induced by ultra-short infrared pulses covering only a few photon cycles. In
particular, we investigate the impact of the Carrier-Envelope Phase (CEP) of
the laser pulse which plays an increasingly large role for decreasing pulse
length. As key observable we look at the asymmetry of the angular distribution
as function of kinetic energy of the emitted electrons. The focus of the
present study lies on the system dependence of the reaction. To this end, we
study two very different systems in comparison, an Ar atom and the Na9+
cluster. The study employs a fully quantum-mechanical description of electron
dynamics at the level of Time-Dependent Density Functional Theory (TDDFT). We
find a sensitive dependence on the system which can be related to the different
spectral response properties. Results can be understood from an interplay of
the ponderomotive motion driven by the external photon field and dynamical
polarization of the system.
