The theory of the continuous absorption spectrum of bromine

Abstract

The discovery of the complex nature of the visible continuous absorption spectrum of bromine by Acton, Aickin, and Bayliss made it interesting to investigate the continuum theoretically, since the interpretation of the two components that they found to be present is still uncertain. The investigation also provides another application of the potential energy functions and eigenfunctions that were used by Gibson, Rice, and Bayliss in their treatment of the continuous absorption spectrum of chlorine, although the theory has been slightly modified. The experimental data with which the theory is to be compared consist of values at a number of wave-lengths of ε 0 and ε 1 , the absorption coefficients appropriate to the vibrational states v ″ = 0 and 1 respectively, which were determined by an analysis of the temperature variation of the observed absorption coefficient ε. For bromine, the curve of ε 0 against wave number was shown to consist of the sum of the ε 0 curves of two overlapping continua, which arise from separate electronic transitions from the ground state ( 1 ∑ g + ), and which were temporarily designated as A ( λ max . = 4150 A.) and B ( λ max . = 4950 A.). Dirac has shown that the probability per second of the absorption of radiation by an atom from a beam of photons whose intensity is one photon/unit frequency range/cm. 2 /second is k = (8π 3 v /3 hc ) | ( α ′ | D | α ″) | 2 .