Comparison of the simulated correlated parallel momentum spectra with the experimental measurements.^[14] The first row shows the simulated results for NSDI of He in the laser field at the peak intensity of 3.5 × 10¹⁴ W/cm²: (a) excitation-tunneling from all excited states of n = 2 and 3, (b) (e,2e), (c) sum of excitation-tunneling and (e,2e). The second row displays the experimental data: (d) full experimental measurements, (e) spectra excluding (e,2e) and excitation-tunneling, (f) spectra deduced from (d) with (e) deducted. The calculations include the integration over the focal volume of the laser. Adapted from Ref. [39].