This work deals with the effect of injected gas density on the characteristics of the liquid core observed at the exit of the injection element used for cryogenic propulsion. The study was conducted at atmospheric pressure both in water/air and in liquid oxygen/inert gas. The techniques used are visualization, optical fiber probe, and a phase Doppler system. In keeping with our predictions, we show that for a constant momentum flux ratio J between the gas and the liquid, the higher the gas jet density is, the more the gas jet is capable of atomizing the liquid jet efficiently. A correlation of the liquid presence probability (LPP) on the jet axis, which implies notably J and the density ratio between the gas and the liquid, gathers the results obtained in simulation fluids and in a liquid oxygen jet, with good agreement.