W. R. Hindmarsh 
Atomic Spectra [PDF ebook] 
The Commonwealth and International Library: Selected Readings in Physics

Atomic Spectra compiles papers on the highlighted developments in the atomic spectra. This book discusses regularities in spectra emitted by monatomic gases that lead to an understanding of the structure of atoms and discovery of the principles that govern the behavior of matter on the atomic scale. This compilation includes Rydberg’s famous account of the series of spectral lines; Weisskopf and Wigner’s papers on natural line-width; and Bethe’s study on the Lamb shift of energy levels. Papers dealing with the spectra of atoms with more than two electrons in the valence shell and continuous spectra of atoms are not included. This publication is useful to students intending to gain knowledge on the atomic spectra.