We report the results of a battery of experiments to determine the origin of ${\mathrm{Na}}_2^{+}$ produced by crossed sodium beams in the presence of intense optical radiation. The principal mechanism appears to be atomic collision combined with photon absorption. The characteristics of long-range optical collisions are compared with those expected from collisional resonances.

• Received 15 October 1982

DOI:https://doi.org/10.1103/PhysRevA.27.2817