Fig. 2: The response matrix for the photoelectron spectrometer (PES) array.

The response matrix, R (Eqn. (2)), was computed with data from six electron time-of-flight spectrometers (eToFs), the corresponding photon spectra from the variable-line spacing (VLS) spectrometer and all the available shots N = 15,337. Each of the eToFs produces a distinct curve (red line) mapping the time-of-flight to the photon energy measured by the VLS spectrometer. The intensity at specific photon energy, i.e., spectrograph pixel, is comprised of contributions (positive and negative) from each of the six eToFs.