Multiphoton Double Ionization of Helium at 394nm - a Fully Differential Experiment

Abstract

We report on a kinematically complete experiment on strong field double ionization of helium using laser pulses with a wavelength of 394\,nm and intensities of $3.5-5.7\times 10^{14}W/c{m}^2$. Our experiment reaches the most complete level of detail which previously has only been reached for single photon double ionization. We give an overview over the observables on many levels of integration, starting from the ratio of double to single ionization, the individual electron and ion momentum distributions over joint momentum and energy distributions to fully differential cross sections showing the correlated angular momentum distributions. Within the studied intensity range the ratio of double to single ionization changes from $2\times 10^{-4}$ to $1.5\times 10^{-3}$. We find the momentum distributions of the ${\mathrm{He}}^{2+}$ ions and the correlated two electron momentum distributions to vary substantially. Only at the highest intensity both electrons are emitted to the same direction while at the lowest intensity back-to-back emission dominates. The joint energy distribution of the electrons shows discrete structures from the energy quantization of the photon field which allows us to count the number of absorbed photons and thus access the parity of the final state. We find the energy of the individual electron to show a peak structure indicating a quantized sharing of the overall energy absorbed from the field. The joint angular momentum distributions of the two electrons show a highly directed emission of both electrons along the polarization axis as well as clear imprints of electron repulsion. They strongly change with the energy sharing between the electrons. The aspect of selection rules in double ionization which are also visible in the presented dataset has been subject to a preceding publication [1].

arXiv comment10 pages, 13 figures, submitted to PRA

References in corpus (8)

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• Streaking temporal double slit interference by an orthogonal two-color laser field
• Ejection of quasi-free electron pairs from the helium atom ground state by single photon absorption
• Double photo-electron momentum spectra of Helium at infrared wavelength
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Cited by in corpus (7)

• Slingshot non-sequential double ionization as a gate to anti-correlated two electron escape
• Electron double-emission spectra for Helium atoms in intense 400 nm laser pulses
• Three-electron correlations in strong laser field ionization: Spin induced effects
• Polarization tagging of two-photon double ionization by elliptically polarized XUVs
• Strong-Field Double Ionization in a Three-Electron Atom: Momentum Distribution Analysis
• Quantum versus semi-classical signatures of correlated triple ionization in Dalitz plots
• Fingerprints of slingshot non-sequential double ionization on two-electron probability distributions