Laser-assisted two-color two-photon double ionization of helium atoms

Direct two-photon double ionization of helium

The role of electron correlation, i.e. the electron-electron repulsion, in non-sequential two-photon double ionization of helium has been widely debated in literature, and the issue is not yet fully resolved. We present total cross sections for this process obtained within a one dimensional model of the helium atom. In our calculations the cross sections are obtained in two ways. Firstly, the t...

Different escape modes in two-photon double ionization of helium

The quadrupole channel of two-photon double ionization of He exhibits two distinctly different modes of correlated motion of the photoelectron pair. The kinematics of the mode associated with the center-of-mass motion favors large total momenta maximized at parallel emission where the interelectron repulsion is strong. In contrast, the mode associated with the relative motion favors large relat...

Two-photon double ionization of helium in the region of photon energies 42-50 eV

We report the total integrated cross-section (TICS) of two-photon double ionization of helium in the photon energy range from 42 to 50 eV. Our computational procedure relies on a numerical solution of the time-dependent Schrödinger equation on a square-integrable basis and subsequent projection of this solution on a set of final states describing two electrons in continuum. Close to the thresho...

Anisotropy parameters in two-color two-photon above-threshold ionization

Phase measurement of resonant two-photon ionization in helium.

We study resonant two-color two-photon ionization of helium via the 1s3p (1)P(1) state. The first color is the 15th harmonic of a tunable Ti:sapphire laser, while the second color is the fundamental laser radiation. Our method uses phase-locked high-order harmonics to determine the phase of the two-photon process by interferometry. The measurement of the two-photon ionization phase variation as...