A continuum light emission extending from the infrared to the ultraviolet has been observed in highly excited Xe and Kr crystals. The light is emitted by an electron plasma with an electron density of about 10 to the 18th per cu cm. The kinetic energies of the electrons correspond to an electron temperature of about 2000 K for a lattice temperature of 15 K (Kr) and 60 K (Xe). This electron plasma represents a case of an extreme thermal nonequilibrium between electrons and the lattice consisting of neutrals and ions.
In time resolved luminescence spectra, taken within the temperature range of 1180 K, the two lowest excited states of rare gas crystals are observed. One of them, the long lived 3 state is identified as the initial state for transient absorption. The transient absorption spectra (1180 K) indicate strong similarities between self-trapped excitons in the crystals and free excimers, but only in the energy region up to 1.5 eV above the lowest excited state 3. Higher energy levels and the continuum states of the self-trapped exciton are strongly influenced by solid state effects. The Journal of Chemical Physics is copyrighted by The American Institute of Physics