Asymmetry of Wigner's time delay in a small molecule

Ionization by an attosecond pulse launches an electron wave packet in the continuum which contains rich information about the pulse, the parent system, and the ionization dynamics. This emission process is not instantaneous in the sense that the electrons take a finite time to leave the potential. This time is closely related to the Wigner time. In this paper we introduce the stereo Wigner time delay, which measures the relative delay between electrons emitted to the left and right in an asymmetric system. We present a theoretical study of the delay in photoemission for a small asymmetric molecular system using the streaking technique. The stereo Wigner time delay shows advantages compared to previous schemes. Our numerical calculation shows that such a measurement removes the infrared laser-Coulomb coupling, which has been problematic in the interpretation of the measured delay in photoemission from atomic systems.