Correlated two-electron dynamics in strong-field double ionization

Vector momenta of electrons and ions have been measured for strong-field (25 fs, 0.25 to 1.0 PW/cm(2)) double ionization of Ar using a reaction microscope.'' Correlated two-electron momentum distributions along the field direction ( P-1parallel to, P-2parallel to) are explored at different transverse momenta P-1perpendicular to of one of the electrons. Whereas a distinct (P-1parallel to, P-2parallel to) correlation, strongly varying with P-1perpendicular to is observed for nonsequential double ionization at small light intensity, only a weak, but still significant correlation is found at large intensity where sequential ionization dominates.