Prospects for Laser Spectroscopy of Ps₂

Recent observations of molecular positronium (Ps2) were based on a correlation between changes in positronium (Ps) lifetime spectra associated with the density of an incident positron beam and the population of a positronium (or positron) surface state. While the evidence for molecule formation is compelling it is nevertheless an indirect observation, and has not provided any information about the properties of Ps2 beyond its likely creation. Here we discuss the prospects for a direct observation via laser spectroscopy of a predicted 1S2P excited molecular state. Such a measurement would provide a direct and unambiguous signal of Ps2 formation and would also allow us to determine some properties of the molecule, namely the lifetime of the excited state and the 1S1S-1S2P energy interval.