Rotationally resolved spectra of Pt?

High-resolution laser-induced fluorescence spectroscopy has been used to investigate the 18 163 cm21 band of Pt2 in a supersonically cooled molecular beam. Rotational constants of the ground and excited states were extracted from the rotationally resolved spectrum and determined to be B0'=0.031 754(12) cm-1 and B'0=0.028 672(11) cm-1, respectively. These values correspond to ground- and excited-state bond lengths of r"0=2.33297(44) ? and r'0=2.455 16(47) ?, respectively. Nuclear spin statistics that are observed in the spectrum demonstrate that the ground state is of either 0g 1 or 0u 2 symmetry. Of these, 0g 1 is by far the more probable. Comparisons with Au2 are made, suggesting that it may be appropriate to consider Pt2 as having a double bond.