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We use photoassociation of ultracold Na to study transitions from free atoms to bound molecules. We obtain rovibrational spectra of the 1g, the 0+u, and, for the first time, the 0−g ‘‘purely long-range’’ state of Na2, all of which dissociate to Na(3 2S1/2)+Na(3 2P3/2).

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This paper surveys the ongoing physics experiments at the Electron Beam Ion Trap (EBIT) facility at NIST, with particular attention paid to the underlying physical principles involved. In addition, some new data on the performance of our EBIT are presented, including results related to the determination of the trap width, ion temperature, and number of highly charged ions in the trap.

We demonstrate a number of two-colour spectroscopy techniques where the first step is the photoassociation of laser-cooled and trapped sodium atoms to form bound states of Na 2 . High-resolution (∼ 0.001 cm −1 ) spectra of Na 2 are obtained. Spectra of the 0 − g (3S + 3P 3/2 ) 'purely long-range' state demonstrates the use of two-colour spectroscopy to open up an ionization channel for detecting the occurrence of photoassociation. The utility of photoassociation as a technique for producing cold molecular samples in a well defined rovibrational state is demonstrated with spectra showing bound → bound and bound → free (Condon internal diffraction) transitions after the photoassociation. Starting from states in the 0 − g and 1 g (3S + 3P 3/2 ) potentials, these transitions include upward transitions to autoionizing potentials dissociating near 3P + 3P and downward transitions back to the 3S + 3S ground-state potentials. Spectroscopic constants for six levels of a doubly excited 1 u state of Na 2 are given.