We report the determination of the absolute rate constant of ${\mathrm{Na}}_2^{+}$ production by associative ionization collisions between crossed beams of Na $3{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ atoms. New measurement techniques greatly improve the accuracy of rate-constant determinations in crossed-beam experiments. We find the rate constant to be (1.8±0.7)×${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^3$${\sec }^{-1\mathrm{}}$. This value is appreciably larger than many of those previously reported.

• Received 31 January 1983

DOI:https://doi.org/10.1103/PhysRevA.28.604