Generation of a single attosecond x-ray pulse

The feasibility of generating a single attosecond x-ray pulse is demonstrated. This can be achieved by generating high-order harmonics of a light pulse with a variable ellipticity and a relative spectral width Δω/ω ≈ 0.04. A way is proposed for generating such a pulse by linear optical methods from a linearly polarised bandwidth-limited laser pulse. An attosecond x-ray pulse generated from such a laser pulse may then be separated in the far-field diffraction zone from the overall field by a system of apertures.