Helium atom accurate treatments

The Bohr model gave the correct energies for the hydrogen atom but failed when applied to helium. Hence, in the early days of quantum mechanics, it was important to show that the new theory could give an accurate treatment of helium. The pioneering work on the helium ground state was done by Hylleraas in the years 192 1930. To allow for the effect of one electron on the motion of the other, Hylleraas used variational functions that contained the interelectronic distance ri2- One function he used is... 

This work provides an accurate and complete treatment of the collision of a multicharged ion on a neutral atom target — here the helium atom — taking into account both ground and metastable states. 

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