It is now clear that excitations from the Ga-3d core level into the empty surface states are highly excitonic in nature. These transitions can be studied by partial yield or low-energy electron-loss spectroscopy, and in the past their disappearance with oxygen exposure has been attributed to oxygen bonding on surface Ga atoms and destroying the empty surface states. By combining partial yield, ultraviolet photoemission, and soft x-ray photoemission data, it is shown that this disappearance is not due to oxygen bonding on Ga atoms but due to exciton extinction from oxygen-induced changes in the surface electronic structure at very low coverages.