4.2 The quantum defect 63−−−−−−
Fig. 4.2The energies of the s, p, d and
f configurations in sodium. The energy
levels of hydrogen are marked on the
right for comparison. The guidelines
link configurations with the samento
show how the energies become closer to
the hydrogenic values aslincreases, i.e.
the quantum defects decrease so that
δl 0 for f-electrons (and for the con-
figurations withl>3thathavenot
been drawn).δs=1. 35 ,δp=0. 86 ,δd=0. 01 ,δl 0 .00 for l> 2.There is a small variation withn(see Exercise 4.3). Having examined
the variation in the quantum defects with orbital angular momentum
quantum number for a given element, now let us compare the quantum
defects in different alkalis. The data in Table 4.1 show that the alkalis
have similar ionization energies despite the variation in atomic number.
Thus the effective principal quantum numbersn∗ =(13.6eV/IE)^1 /^2