Associative ionization with cold Rydberg lithium atoms

Rydberg-atom-Rydberg-atom associative ionization was measured in lithium at 85 K for principal quantum numbers 3, 5, and 9. The very high rate constants, up to 10 to the -7th cu cm/s, were modeled by considering the binding between the ion and the Rydberg atom which results from an initial ionizing collision. A search for evidence of ion pair production yielded an upper bound on its rate constant of 3 x 10 to the -10th cu cm/s for n = 9. Lithium negative ions observed in the experiment were produced by attachment. (Author)