Vibrational State Distribution ofNa2+Ions Created in Ultracold Collisions

Abstract
The vibrational distribution P(v) of Na2+ ions created in ultracold collisions in a magneto-optical trap has been determined. Only two vibrational states with v=2and3 are populated and we find P(2)=0.29±0.02 and P(3)=0.71±0.02. The results provide conclusive evidence that the ionization mechanism is photoassociative autoionization, and not photoassociative photoionization, and will form a fundamental test for the theoretical description of the process.