Collective multi-electron tunneling ionization in strong fields

The process of multi-electron tunneling in strong fields has, to the authors' knowledge, never been considered in detail. In principle, it is one possible mechanism for multi-electron ionization in strong laser fields. We have carried out first analytical and numerical studies of this novel process, that prove the existence of collective tunneling but fail to explain the laser experiments. As a second result, we present an empirical modification of the multi-electron tunneling formula that leads to an astonishing agreement with laser experiments over a wide range of parameters, even if only for linear laser polarization