CORRELATED KELDYSH-FAISAL-REISS THEORY OF ABOVE-THRESHOLD DOUBLE-IONIZATION OF HE IN INTENSE LASER FIELDS

We have developed a correlated Keldysh-Faisal-Reiss theory of laser-induced double ionization of a two-electron atom. The basic N-photon T matrix and the expression for N-photon triple-differential rates or cross sections (TDCS's) are derived. The theory is applied to investigate the TDCS's for very-high-order multiphoton double ionization of He with lasers of wavelength lambda = 248 nm and lambda = 617 nm. Comparison with the uncorrelated results reveals a dramatic influence of the final-state e-e correlation on the above-threshold TDCS's to be measured in coincidence experiments in intense laser fields. The limiting case of the TDCS's for weak-field double ionization of He by a synchroton photon is also investigated; the results confirm the earlier theoretical findings and recent experimental results in that case.