The Structure of Emission Lines

A method for obtaining the intensity distribution in a spectral line is derived from Dirac's quantum theory of the radiation field. The calculations are carried out for the case of emission from a first excited state (resonance line) and show that the intensity of frequency ν is, in this case, proportional to 1[4π²(ν₀-ν)²+(A·2)²] were A is the rate at which atoms are leaving the upper state and ν₀ is the frequency of the transition. The half-width is therefore 12π times the Einstein probability coefficient for spontaneous transition to the lower state. The more general case where the lower state has a finite life time is not treated.A general method for the treatment of radiation problems, which is essentially Weyl's modification of Dirac's method, is briefly described.