High resolution electronic band spectral studies of the GaI molecule

The emission band spectrum of the GaI molecule, lying in the region 3800–4200A and attributed to two overlapping transitions (A0⁺-X0⁺ and B1-X0⁺), has been studied under high resolution in the 3rd order of a 10.5 m Ebert grating spectrograph at a dispersion of 0.18/mm. Isotopic shifts of the ⁷¹GaI and ⁶⁹GaI molecules are calculated for various bands. They are found to agree with experimentally measured values, thereby confirming the vibrational assignments. The reversal of shading of various branches, belonging to one band and leading to the formation of extra heads, has been investigated. Making use of the rotational constants of the ground state (X0⁺) obtained from microwave spectral studies, the rotational constants of the excited A0⁺ and C1 states have been evaluated. Electronic configurations, potential energy curves and dissociation products are discussed.