  Some features of the field induced phase transition accompanied by the vacuum
creation of an electron-positron plasma (EPP) in strong time-dependent electric
fields have been discussed in the work [1] in the domain of the tunneling
mechanism ($\omega \ll m$, where $\omega$ is the characteristic frequency of
the external field and $m$ is the electron mass). In the present contribution
the features of the this process will be considered in the few photon domain
where $\omega \sim m$. We observe a narrowing of the transient domain of the
fast oscillations and, mainly, a considerable growth of the effectiveness of
the EPP production. Under these circumstances, we see an increase of the
effectiveness of the EPP creation in the particular case of a bifrequent
excitation, where both mechanisms (tunneling and few photon) act simultaneously
[2,3].
