Experimental test of recollision effects in double ionization of magnesium by near-infrared circularly polarized fields

We report experimental results on correlated double ionization of magnesium (Mg) by near-infrared (0.8- and $1.03\text{\ensuremath{-}}\ensuremath{\mu}\mathrm{m}$) circularly polarized laser fields. With $0.8\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$, we confirm the recollision interpretation of the observed ``knee'' structure of Mg [Gillen et al., Phys. Rev. A 64, 043413 (2001)], even though the experiments are performed in the multiphoton regime. Our experiments show that, even in the multiphoton regime, which is normally thought to be a purely quantum-mechanical territory, some ionization phenomena can still be understood classically.