INVESTIGATIONS ON THE PRODUCTION KINETICS OF IONIC ALKALI RARE-GAS EXCIMERS

Ionic rare gas alkali excimers Rg+A were produced by exciting Rg/A mixtures in a buffer gas atmosphere by means of an ion or electron beam. As a representative candidate the formation of Kr+K decaying at 135 nm was investigated. The rate constant k(He) for the main reaction Kr+ + K --> Kr+K was determined varying the buffer gas density [He] between 10(17) and 10(20) cm-3. Values between k(He) = 1 X 10(-11) and 5 X 10(-10) cm3 s-1 were observed. At high buffer gas densities the quantum yield eta(q) for the emission of the 135 nm radiation depends on the ratio [K]/[Kr]. At the optimum value, [K]/[Kr] = 0.06, an absolute yield of eta(q) = 1.5% was obtained. Up to a deposited energy of 3 mJ/cm3 the quantum yield is independent on the excitation density. For neon as buffer gas the rate constants k(Ne) are smaller by about a factor of 3, while the efficiency is only slightly less than for He. Kr+K is split into five fine structure states. The quenching of these states by krypton and buffer gas causes the low quantum yield.