Fig. 2: Overview of the experimental quantities that give access to changes of the Wigner time delay.
From: Angular dependence of the Wigner time delay upon tunnel ionization of H2
a Electric field E(t) and negative vector potential −A(t) for one cycle of the co-rotating two-color (CoRTC) field comprised of a high-intensity pulse (central wavelength of 390 nm) and a low-intensity pulse (central wavelength of 780 nm). The helicities of the two pulses are indicated with arrows. Using that the ion’s momentum vector \({\boldsymbol{p}}_{{\mathrm{H}}^ + }\) always points along the molecular axis allows for the measurement of the orientation of the molecular axis. \({\boldsymbol{p}}_{{\mathrm{H}}^ + }\) is measured in coincidence with the electron momentum vector pelec. As illustrated, β is the electron emission angle relative to the molecular axis in the polarization plane. b Measured electron momentum distribution in the polarization plane of the laser’s electric field: ATI and SB peaks are half-rings which are spaced by the energy of a photon of the weaker laser pulse at 780 nm (1.6 eV). The most probable electron emission direction, α(β), is indicated for the first ATI peak. c Changes in the most probable electron angle, Δα, as a function of β are presented for each ATI/SB peak separately. αmean is determined for every energy peak independently as the mean of α(β) over all β (see Fig. S1). The values for the vector potential and the electron momentum are in atomic units (a.u.). The error bars show the standard deviation of the statistical errors.
