We have observed the spectrum of long range molecular states of singly
excited Na2 formed by photoassociation during ultracold associative i
onization collisions of laser-cooled Na atoms. The low kinetic energy
of the collision allows us to obtain very high resolution spectra and
to observe states close to the dissociation limit. The spectrum shows
regular vibrational series characteristic of the 1/R3 long range porti
on of the 1g potential (asymptotically S1/2+P3/2) as well as molecular
hyperfine structure within these peaks. We extract potential paramete
rs and compare with recent theory.