Section III, 1921 [131] Trans. R.S.C. 



Selected Radiations Emitted by Specially Excited Mercury Atoms 

 By H. J. C. Iretox, M.A. 

 (Read May Meeting, 1921)* 

 I. Introduction 



Investigation of the relationships among the frequencies of the 

 spectra of the elements has shown that the members of a spectral 

 series are given bv an equation of the form 



v=iX,S)-{Y,P) 

 and the form of this equation suggests, in the light of the quantum 

 theory, that the frequencies of the members of the series are pro- 

 portional to differences in the energy possessed by the entity which is 

 radiating the wave lengths in question. 



If we suppose that those radiations emitted by an atom which 

 constitute spectral series arise from the displacement of electrons, 

 in atoms, it would follow from the form of the equation given above 

 that (X, S) and ( Y, P) may be taken to be proportional to the energy 

 possessed by the atom with the electron in the two positions or states 

 between which the displacement takes place. We have then in the 

 series frequency formulae for the atoms of any element, values for 

 the energy which correspond to the various states in which those 

 electrons in the atoms may be which contribute by their displacement 

 to the radiation emitted. The values of {X, S) and (F, P) taken from 

 the frequency formulae of the spectrum of an element can be arranged 

 in order of magnitude, and in this way be used to throw some light 

 on the question of the configuration of the extra nuclear electrons of 

 an atom emitting radiation. 



This method has been suggested by Birge and has been applied 

 by Foote and Meggers^ to the Caesium atom. An application of 

 the method to the atom of mercury, involving the use of data from 

 known spectral series for this element, is shown in Fig. 1. According 

 to this diagram, it will be seen that the wavelength X= 1849.6 A.U. 

 may arise from electrons passing from the position of (2, P) energy 

 to that of (1.5, S) energy. The second member of this principal 

 sjngle line series may be represented by electrons passing from the 

 (3, P) position to the (1.5, S) one. The series (2, P) — {m, S) where 



* Comn unicated by Professor J. C. McLennan, F.R.S. 

 1 Scientific Papers No. 386. Bureau of Standards. 

 —31 



