Photoelectron Spectroscopy of AuO- and AuS-

The 364 nm photoelectron spectra of AuOand AuShave been measured. The electron affinities of AuO and AuS have been determined to be 2.374 ( 0.007 and 2.469 ( 0.006 eV, respectively. The electronic ground states of the neutral diatomics are Πi states, and the spin-orbit splitting between the XΠ1/2 and Π3/2 states is 1440 ( 80 cm-1 for AuO and 1280 ( 60 cm-1 for AuS. A 590 ( 70 cm-1 vibrational peak built off the Π1/2 origin of the AuO spectrum is clearly detected, while the corresponding peak built off the Π3/2 origin is barely detectable. The corresponding 400 ( 30 cm-1 vibration in the AuS spectrum shows the opposite behavior, with the Π3/2 showing the stronger vibrational activity. Franck-Condon analyses of the spectra establish that the equilibrium bond length of X1Σ+AuO(AuS-) differs from the average bond length of the two spin-orbit states of AuO (AuS) by -0.015 ( 0.008 Å (+0.018 ( 0.007 or +0.007 ( 0.007 Å). These bond length relations reflect different extent of relativistic effects between the anions and the neutrals. The intensity of the XΠ1/2 origin peak is significantly greater than that of the XΠ3/2 origin peak in both AuO and AuS. These features are the results of strong second-order spin-orbit coupling between the X1Σ+ state and A Π0 state in the corresponding anions. The bond length of X1Σ+AuOhas been determined to be 1.899 ( 0.006 Å based upon the bond length of XΠ3/2AuO.