Double Photoelectron Momentum Spectra Of Helium At Infrared Wavelength

Double photoelectron momentum spectra of the helium atom are calculated ab initio at extreme ultraviolet and near-infrared wavelengths. At short wavelengths two-photon double-ionization yields, two-electron energy spectra, and triply differential cross sections agree with results from recent literature. At the near-infrared wavelength of 780nm the experimental single-to-double-ionization ratio is reproduced up to intensities of 4×1014W/cm2, and two-electron energy spectra and joint angular distributions are presented. The time-dependent surface flux approach is extended to full 3+3 spatial dimensions and systematic error control is demonstrated. We analyze our differential spectra in terms of an experimentally accessible quantitative measure of correlation.

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