THE A'1(U)[-X0(+)(G) SYSTEM OF GOLD DIMER

The A'1(u) <-- X0(g)(+) system of gold dimer was studied at a Doppler- limited resolution of 120 MHz. The molecules were prepared by laser va porization of a gold rod and cooled by supersonic expansion in helium. Rotationally resolved spectra of the (0,0), (1,0), and (2,0) bands we re recorded using a continuous wave ring dye laser to excite fluoresce nce. The Ohm = 1(u), symmetry of the A' state was confirmed, and the f ollowing salient molecular parameters obtained: nu(00) = 18 129.8336(1 0) cm(-1); B-0 = 0.026362(6) cm(-1) (2 sigma error bounds). All three excited stale vibrational levels were found to be subject to rotationa l perturbations. The perturbation of the nu' = 2 level was analysed in detail, and is believed to be caused by interaction with a high-lying vibrational level of the a(3) Sigma(u)(+)(1(u)) state. The location o f this level was used to revise the dissociation energy ofthe ground s tate of gold dimer (D-0(0)(X0,(+)(g))),which is now computed to lie in the range 18 562-18 639 cm(-1) (2.301-2.311 eV).