This rather daunting expression can be multiplied out, to give four terms:
Click here to return to the list of online lectures
Click here to return to the previous Section
Click here to go on to the next Section
This page created by Jeremy Harvey, Bristol, 2000.
![\[ \begin{array}{llll}
\iint \chi_i(\mbox{x}_1)\chi_j(\mbox{x}_2) {\displaystyle \frac {1}{r_{12}}}
\chi_i(\mbox{x}_1)\chi_j(\mbox{x}_2) d\mbox{x}_1d\mbox{x}_2 \\
-\iint \chi_i(\mbox{x}_1)\chi_j(\mbox{x}_2) {\displaystyle \frac {1}{r_{12}}}
\chi_i(\mbox{x}_2)\chi_j(\mbox{x}_1) d\mbox{x}_1d\mbox{x}_2 \\
-\iint \chi_i(\mbox{x}_2)\chi_j(\mbox{x}_1) {\displaystyle \frac {1}{r_{12}}}
\chi_i(\mbox{x}_1)\chi_j(\mbox{x}_2) d\mbox{x}_1d\mbox{x}_2 \\
\iint \chi_i(\mbox{x}_2)\chi_j(\mbox{x}_1) {\displaystyle \frac {1}{r_{12}}}
\chi_i(\mbox{x}_2)\chi_j(\mbox{x}_1) d\mbox{x}_1d\mbox{x}_2
\end{array}
\]](test_1.gif)