  In the article an ultracold electron-ion plasma created by photoionization of
cooled atoms is investigated. We obtained analitical expressions for
non-ideality parameters which establish due to correlation heating. In the work
the nearest neighbour and the Wigner-Seitz cell approximations were used, the
recombination heating of electrons was taken into account. We have got a good
agreement with the experiment results. The possibility of creation of strongly
non-ideal electron subsystem has been shown and conditions of this process have
been determined.
