Quantum theory of single subfemtosecond extreme-ultraviolet pulse measurements

Abstract

Recently the initial measurements of single attosecond pulses with laser-dressed single-photon XUV ionization of gas atoms were reported. Determination of the extreme-ultraviolet (XUV) pulse duration from the electron spectrum is based on a classical theory. Although classical models are known to give a qualitatively correct description of strong laser–atom interaction, the validity range for accurate determination of subfemtosecond pulses must be scrutinized by quantum mechanical analysis. We establish a theoretical framework for the accurate temporal characterization of attosecond XUV pulses by using a Fourier–Bessel expansion of the XUV electron spectrum under the strong field approximation and a semiclassical derivation, setting earlier results on a rigorous theoretical footing. Our analysis reveals an improved scheme that is by more than an order of magnitude more efficient than the one used so far and allows for direct experimental discrimination between single and multiple attosecond pulses.