A simple description of the spectra of confined hydrogen, helium, and lithium

A simple description of the spectrum of confined hydrogen atom is obtained in terms of an scheme involving interpolation between the expressions for large and small values of the confining radius. Satisfactory agreement is shown to exist between the eigen energies thus calculated and exact values. The scheme is extended for helium and lithium. With the simulation of interaction between the electrons by a screened nuclear charge, some energy levels are deduced for the confined helium and lithium