radius, the expectation of <IMG
 WIDTH="46" HEIGHT="36" ALIGN="MIDDLE" BORDER="0"
 SRC="img86.png"
 ALT="$\sum_i r_i^2$">.
</LI>
<LI>The dipole-dipole operator, the expectation of <!-- MATH
 $(\sum_i r_i)^2$
 -->
<IMG
 WIDTH="63" HEIGHT="36" ALIGN="MIDDLE" BORDER="0"
 SRC="img87.png"
 ALT="$(\sum_i r_i)^2$">,
</LI>
<LI>The Isotope shift parameter, <!-- MATH
 $S= - \sum_{i<j} \nabla_i\cdot \nabla_j$
 -->
<IMG
 WIDTH="144" HEIGHT="34" ALIGN="MIDDLE" BORDER="0"
 SRC="img88.png"
 ALT="$S= - \sum_{i&lt;j} \nabla