Excimer formation mechanism in gaseous krypton and Kr/N mixtures.

A new approach for the understanding of the energy relaxation dynamics of excited atoms involving a long-lived molecular precursor is presented here for krypton. Excitation of the gas close to the 5 s[3/2] metastable atomic level ( E − E< kT) is achieved with an intense VUV laser source (I ≈ 10 photon/pulse) realized by resonantly enhanced 4-wave mixing (2ω + ω) in room temperature mercury vapor ( N ≈ 10 at./cm). The decay of the II. continuum luminescence (145 nm) is studied. In the pressure range 200-500 mbar, decay rates depend linearly on pressure but have a negative zero-pressure intersect. We show here that this result can be understood as an effect of the exchange of energy between two different 'reservoirs' of atomic (5 s[3/2]) and molecular (1) nature, and can be an inherent peculiarity of the recombination kinetics of excited atoms with several product channels. The efficiency of the model is checked for the Kr/N system. Rate constants for relaxation processes are determined in pure krypton and in Kr/N mixtures. [ABSTRACT FROM AUTHOR]