Correlation of momenta of electrons and the nucleus in atoms

The expectation values of cross products of the momenta of electrons and pr oducts of the momentum of an electron and the momentum of the nucleus, whic h describe the correlation of moments of the particles in an atom, are cons idered by allowing for the conservation of total momentum and for the ident ity of electrons. It is shown that these expectation values are expressed i n terms of the average values of the squares of the momenta of electrons an d the nucleus, which determine the kinetic energy of an atom. The expectati on values of products of the momenta of particles are calculated for the ne gative ions H-infinity(-), T-, D-, H-, mu(-), and Ps(-), the helium atom, a nd the hydrogen molecular ion. The dependence of angular correlation in the motion of electrons on the nuclear mass is discussed. (C) 2000 MAIK "Nauka /Interperiodica".