Xenon is added to the axial channel of an argon inductively coupled plasma (ICP) at doses up to 1.5% of the aerosol gas flow. Emission is collected from the gas flowing into the sampling orifice of a mass spectrometer (MS). These Xe doses have little effect on the electron density n e or on the intensities of Fe (I) emission lines. Certain Fe (II) lines are enhanced when Xe is added, particularly those from Fe + states that can be populated by near-resonant charge transfer between Xe + and neutral Fe. Calculations based on measured values of n e indicate that Xe + should be present at densities of up to 7 10 1 4 cm - 3 , which should be sufficient Xe + to drive the proposed charge transfer reactions.