Amplified spontaneous emission over the XeF(D→X) transition in solid Kr

XeF doped solid Kr represents a novel solid state exciplex laser. A net gain in excess of 100 cm−1 and a superradiant beam of 5 mrad divergence are observed over the XeF(D→X) transition at 301 nm, when free standing crystals of XeF doped Kr are optically pumped near the XeF(D←X) absorption maximum at 260 nm. Superlinear dependence of gain on pump intensity and low divergence of the amplified beam are taken as evidence for self-focusing. The XeF(D) state is effectively isolated from the lower manifold of charge transfer states in solid Kr, which includes XeF(B,C) and (KrXe)+F−.