in which the Hamiltonian operator takes on the form appropriate to the particular system. In the case
of the helium atom, there are two electrons, each of which has kinetic energy and is attracted to the
2 nucleus. However, there is also the repulsion between the two electrons. With reference to Figure
2.7 , the attraction terms can be written as 2e
2 / r 1 and 2e
2 / r 2 . The kinetic energies can be represented
as
1
2
mv 1
2 and
1
2
mv 2
2 , which in operator forms are written as (
2 /2 m )
1
2 and (
2 /2 m )
2
2 . However,
we now must include the repulsion between the two electrons, which gives rise to the term e
2 / r 12 in
the Hamiltonian. When the complete Hamiltonian is written out, the result is