Band spectrum of aluminium bromide (AlBr)

Abstract

Our knowledge of the band spectra of the diatomic halides of Group III of the Periodic Table is confined at present to boron chloride (BCl) and aluminium chloride (AlCl). Whilst the data concerning BCl are fragmentary and uncertain, the vibrational structure of the AlCl molecule has recently been investigated by Mahanti and by Bhaduri and Fowler. An examination of known halide spectra shows that for a given positive radical the spectra all lie in the same wave-length region and are usually of the sequence type. With increasing halogen mass the system origin moves towards longer wave-lengths and the corresponding vibration frequencies progressively decrease. To illustrate these points, the relevant data for the calcium halides is shown in Table I, calcium being chosen as being the nearest element to aluminium whose halide spectra have been investigated.