NONSEQUENTIAL DOUBLE-IONIZATION - MECHANISM AND MODEL FORMULA

Unexpectedly large probability of laser-induced nonsequential double i onization of He had been observed experimentally. We have recently sug gested a mechanism of energy sharing via e-e correlation, based on the leading Feynman diagram of the process, obtained from the Intense-Fie ld Many-Body S-Matrix Theory. In this paper we derive a simple model f ormula for the total rate of the process by extending this diagram to all orders and summing them approximately. Comparisons of the predicti ons of the model with the data in He at 780 nm over a wide range of in tensity by Walker et al. (1994) show a remarkably good agreement for b oth single and double ionization rates per atom. It is found that this is due to the simultaneous influence of intermediate rescattering, fi eld-induced energy boosting, and e-e correlation during the process.