Treatments for Simple Atoms

The general discussion of Section 30, which is essentially a perturbation calculation, is not capable of very high accuracy, especially since it is not ordinarily practicable to utilize any central field except the coulombic one leading to hydrogenlike orbital functions. In this section we shall consider the application of the variation method (Sec. 26) to low-lying states of simple atoms such as lithium and beryllium. This type of treatment is much more limited than that of the previous section, but for the few states of simple atoms to which it has been applied it is more accurate. 

2 This configuration gives the same interval ratios as np2, only the absolute energy being changed by the presence of the closed shells. 

3 As mentioned in Section 5a, term values are usually given in cm-1 and are measured downward from the lowest state of the ionized atom. Hence the largest term value represents the lowest energy level. 

The principles involved are exactly the same as those discussed in Section 26 and applied to helium in Section 29c, so we shall not discuss them further but instead study the different types of variation functions used and the results achieved. 

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