The production of high-momentum electrons in double ionization helium by near-infrared lasers is investigated using three-dimensional classical ensembles. nucleus' role examined systematically adjusting the nuclear potential. primary source high-energy found to be backscattering off nucleus at recollision. Recollision excitation with unbound electron especially important. It shown that recollision before next field maximum can lead a correlated pair.

The production of anticorrelated (back-to-back) electrons in double ionization atoms by lasers at 483 or 800 nm is examined with 3D classical ensembles, for situations which the energy available recollision less than binding energy. Recollision excitation typically leads to unequal electron energies. more energetic most often drifts into backward direction, whereas other may be likely drift forward direction. That ionizes late first laser maximum after early second maximum.

Longitudinal momentum spectra and electron drift directions are considered for several laser wavelengths in non-sequential double ionization of helium using three-dimensional classical ensembles. In this model, the familiar doublet wavelength 800 nm intensities order 5 × 1014 W cm−2 becomes a triplet 1314 nm, then 2017 nm. The results explained based on whether post-ionization impulse from backward one or both electrons.

Fully classical three-dimensional ensembles are examined under conditions of nonsequential double ionization and shown to have trajectories in which both electrons apparently ionize only one electron bound the nucleus after laser pulse. These feature recollision excitation with subsequent over-the-barrier at about maximum. The ``ionized'' oscillates field but has small enough drift velocity be recaptured turnoff. Whether recapture can occur is extreme sensitivity ionization.

The nonsequential double ionization (NSDI) yield and final electron-electon correlation are examined for a laser wavelength of $800$ nm over wide range intensities, using three-dimensional fully classical models. It is shown that in the transition region between NSDI sequential ionization, turn-on stage recollisions can lead to having majority anticorrelated (back-to-back) electron pairs.

A classical ensemble is employed to investigate double ionization of helium for laser wavelength 390 nm and intensity $1.1\text{ }\text{PW}∕{\text{cm}}^{2}$, below the threshold recollision impact ionization. Significant numbers trajectories that lead electron energy above $2{U}_{p}$ are shown be present feature a time delay between final Processes through which nuclear forces combine give an identified.

Diatomic potentials for krypton are computed and also probed experimentally. For a probe-laser wavelength near $811$ nm, several strong dipole-dipole interactions produce purely-long-range potential wells in the singly excited manifold of ($s+p$) doubly ($p+p$) ($s+d$) potentials. Evidence resonant photoassociation into bound states these is observed emission ions ultraviolet photons from magneto-optically trapped cloud.

We employ 3d classical ensembles to study Non-Sequential Double Ionization (NSDI) of atoms by strong laser fields at visible and infrared wavelengths. consider in particular the wavelength dependence final electron drift directions net momentum spectra parallel polarization. find that as is increased spectrum transitions from a singlet doublet, then triplet, finally back doublet. also show electrons escape central potential-energy well during pulse may nonetheless be bound nucleus after turnoff.

Photoassociation spectra for purely long-range (PLR) krypton molecules are both computed and measured. The photoassociation laser is tuned just red of the 5s[3/2]2-5p[5/2]2 transition at 810.6 nm, over a frequency range in which fourteen different PLR potential wells support hundreds vibrational bound states. In experiment, light directed into cloud magneto-optically trapped 84Kr atoms, emission ultraviolet photons ions monitored. Peaks these signals observed frequencies within 200 MHz...