Attosecond metrology of the two-dimensional charge distribution in molecules

Photoionization as a half-scattering process is not instantaneous. Usually, time delays in photoionization are on the order of tens of attoseconds. In going from a single atom to a nano-object, one can expect the delay to increase, since the photoelectron scatters over a larger distance. Here we show that this intuition is not correct when comparing three-dimensional and planar molecules. Using attosecond interferometry, we find that the time delays in two-dimensional (2D) carbon-based molecules can be significantly shorter than those of three-dimensional counterparts. The measured time delay carries the signature of the spatial distribution of the 2D hole created in the residual molecular cation, allowing us to obtain its dimensions with angstrom accuracy. Our results demonstrate that the photoionization delay depends on the symmetry and shape of the created hole, as we show by identifying a quadrupole contribution in the measured delay of 2D molecules.