The wave function of the system “electron + atom” depends upon electronic coordinates r1 ... rN and spin projections μ1 ... μN. It should be antisymmetric with respect to the permutation of any pair riμi and rkμk. Denoting by one quantity xi all variables riμi and by Pik the permutation operator, we have $$ {p_{ik}}\Phi ( \ldots ,{x_i} \ldots ,{x_k} \ldots ) = -\Phi ( \ldots ,{x_i} \ldots ,{x_k} \ldots ). $$ (1.1) The function Φ is an eigenfunction of the Hamiltonian operator H $$ H\Phi = E\Phi $$ (1.2) where H in the nonrelativistic approximation has the form $$ H = -{1 \over 2}\mathop \sum \limits_i {\Delta _i} -\mathop \sum \limits_i {Z \over {{r_i}}} + \mathop \sum \limits_{i < j} {1 \over {\left| {{r_i} -{r_j}} \right|}}. $$ (1.3)