Extended Data Fig. 3: Gas-phase iodine/helium measurements.
a, Unstreaked XUV photoelectron spectra of iodoethane (red) and an iodoethane/helium mixture (blue) recorded at 105 eV central photon energy. Electrons emitted through the N4,5VV Auger process are spectrally separated from all timed photoelectron peaks. b, Relative I4d−He1s photoemission delay for different mixture compositions of iodoethane and helium. Shown are individual measurements (blue circles), linear regression (red line) and the 95% confidence interval of the regression (shaded area). c, Histograms (blue) of the individual relative photoemission delay measurements (yellow) between He1s and I4d electrons in iodomethane and iodoethane at 105 eV photon energy and normal-distribution fits to the data (red).
