REVERSE ENERGY POOLING IN A K-NA MIXTURE

We report experimental rate coefficients for the reverse heteronuclear energy-pooling collisions K(5D)+Na(3S)-->K(4P)+Na(3P) and K(7S)+Na(3S )-->K(4P)+Na(3P) at thermal energies. Both reactions are exothermic an d very high rates were observed showing that reverse exothermic energy -pooling is an order of magnitude more efficient than the correspondin g forward endothermic energy-pooling reactions. This is in accordance with the general behavior of the exothermic and endothermic energy-poo ling rate coefficients in alkali-metal atoms. In the experiment the po tassium atoms were excited in two steps to either the 5D or 7S state v ia the 4P level using two broadband cw dye lasers. A double-modulation technique has been used to select the fluorescence contributions at t he Na(3P(J)) exit channels due only to the above reactions. The ground -state sodium and potassium atom densities were measured by the absorp tion of Lines from a K-Na hollow-cathode lamp. The measured densities and fluorescence intensities have been used to obtain absolute reverse energy-pooling rate coefficients. The contribution to the rate coeffi cients from other processes are discussed. [S1050-2947(98)03901-8].