Gain on the green (504 nm) excimer band of I₂

Gain on the green excimer band (λ∼504 nm) of the iodine dimer has been observed in electron-beam-pumped mixtures of Ar (or Ne), and hydrogen iodide. A peak gain coefficient of γ>1.1% cm^-1 is measured at 506 nm with a tunable dye laser and the full width at half-maximum (FWHM) of the gain spectrum in Ar diluent is 13 nm. Temporally resolved gain and fluorescence measurements show that the green emission originates from an I₂ ion pair state other than D′. However, strong collisional coupling between the upper states of the UV (λ=342 nm) and green bands and superfluorescence on the UV band (I_{34 2}∼2 MW cm^-2) appear to limit the green gain coefficient to <20% of its small-signal value. Consequently, suppression of superfluorescence on the UV D′→A′ bands of the homonuclear halogens should lead to a new family of excimer lasers with wavelengths extending from the green into the ultraviolet.