Hydrogen-like atom/ion

The hydrogen atom, consisting of a proton and only one electron, occupies a very important position in the development of quantum mechanics because the Schrddinger equation may be solved exactly for this system. This is true also for the hydrogen-like atomic ions He, Li, Be, etc., and simple one-electron molecular ions such as Hj. 

Both the mass—velocity and Darwin terms show unphysical behavior in variational calculations. To demonstrate this, consider a hydrogen-like atom (ion) with a single electron and a nuclear charge Z as a prototype example With a trial wavefunction of the form,... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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