bei48482_FM

Atomic Spectra 259

Appendix to Chapter 7

Atomic Spectra

W

e are now in a position to understand the chief features of the spectra of

the various elements. Before we examine some representative examples,

it should be mentioned that further complications exist which have not

been considered here, for instance those that originate in relativistic effects and in the

coupling between electrons and vacuum fluctuations in the electromagnetic field (see

Sec. 6.9). These additional factors split certain energy states into closely spaced sub-

states and therefore represent other sources of fine structure in spectral lines.

Hydrogen

Figure 7.22 shows the various states of the hydrogen atom classified by their total quan-

tum number nand orbital angular-momentum quantum number l. The selection rule

Figure 7.22Energy-level diagram for hydrogen showing the origins of some of the more prominent

spectral lines. The detailed structures of then2 and n3 levels and the transitions that lead to

the various components of the H line are pictured in the inset.

Excitation

energy, eV

13.6

10

5

0

n = ∞

n = 4

n = 3

n = 2

Hα

n = 1

SPDF

32 S 1 / 2

32 P 1 / 2

32 D 5 / 2

32 D 3 / 2

22 S 1 / (^222) P 1 / 2
22 P 3 / 2
32 P 3 / 2
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