Second-Order Foldy-Wouthuysen Operator Pauli Hamiltonian

Second-Order Foldy-Wouthuysen Operator Pauli Hamiltonian 

For a spherically-symmetric Coulomb potential V r) = —Ze /r, the second-order even term in the Foldy-Wouthuysen expansion, 2 Eq. (11.84), can be cast into the much more familiar form to yield the (relativistic corrections of the) Pauli Hamiltonian, 

These familiar relativistic one-electron operators, whose expectation values often served to define measures for relativistic effects, are only an approximation to the Dirac Hamiltonian of hydrogen-like atoms discussed in chapter 6. Nevertheless, they are also employed in the context of many-electron systems where the one-electron part in / of Eq. (11.1), i.e., Vnuo is approximated solely by the 2 x 2-analogous expressions for Ejoj - - 

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