Photon-induced ionization changes in a neon discharge

Photon-induced voltage changes occur upon irradiation of a gaseous discharge with a tunable dye laser whose wavelength corresponds to an electronic transition of an atomic species in the discharge. The important, and likely dominant, role of ionization changes in producing these voltage changes in demonstrated directly for the first time using a hollow cathode lamp with neon fill gas coupled to a mass spectrometer. Changes in the Ne⁺ concentration are found to correlate with the observed changes in voltage across the discharge when a number of excitec state absorption transitions of neutral neon are irradiated.