Abstract

Associative ionization (AI) in sodium (Na + Na + 2 hv → Na₂⁺ + e−) has been a convenient reaction in which to study excited state collisions under "ultracold" conditions (≤1 mK) because the reaction product is easily identified and collected with high signal-to-noise. Previous studies [1] have revealed evidence of molecular intermediate-state resonances under high-intensity laser conditions. Theoretical analysis [2] has associated this structure with singly- and doubly-excited Na₂ intermediate states. In this work, we present a new technique utilizing a switched magneto-optical trap (MOT) to make clean measurements of the spectrum of associative ionization in a regime where we can identify the peaks as being associated with states of the Na₂ molecule. In addition, our technique reveals new structure in the spectrum of AI versus laser frequency, pointing out the previously unappreciated importance of atomic hyperfine structure in the reaction.

© 1993 Optical Society of America