Excited electronic states of AuF.

We have recorded laser excitation spectra of transitions from the ground X(1)Sigma(+) state of gaseous gold fluoride (AuF) into three excited electronic states in the visible region. We prepared the sample in a dc electric discharge by flowing a dilute mixture of SF(6) in argon through a hollow gold cathode. Two of these electronic states give rise to the previously reported yellow bands of the molecule, for which a rotational analysis is given here for the first time. We have analyzed the (0,0), (1,1), (0,1), and (1,2) bands of these two transitions, which we identify as [17.8]0(+)-X(1)Sigma(+) and [17.7]1-X(1)Sigma(+); their red-degraded (0,0) band heads lie at 563.0 and 566.2 nm, respectively. The (0,0) band of a new, red-degraded [14.0]1-X(1)Sigma(+) transition at 715.1 nm has also been recorded and analyzed. An accurate set of molecular constants of the three excited states as well as the ground state has been determined by least-squares fitting all of the optical data together with measurements made by other workers of the pure rotational spectrum of AuF in its ground state. These constants include the electronic term energies, vibrational frequencies, rotational constants, and Omega-doubling constants. We discuss the nature of these three excited electronic states in terms of the ionic Au(+)F(-) electronic configurations from which they are derived.

Electronic spectrum of TaO and its hyperfine structure.

The B (2)Phi(5/2)-X(1) (2)Delta(3/2)(0,0) band at 778 nm and the C (2)Delta(3/2)-X(1) (2)Delta(3/2)(0,0) band at 737 nm of tantalum oxide (TaO) were recorded by laser excitation spectroscopy using a hollow cathode sputtering source to generate the molecules. The hyperfine structure arising from the (181)Ta (I=72) nucleus was measured at sub-Doppler resolution using the technique of intermodulated fluorescence spectroscopy. The hyperfine structure was assigned and fitted in order to derive accurate values for the magnetic dipole and electric quadrupole interactions. The magnetic hyperfine constant for the ground electronic state was also calculated using the density functional theory as h(3/2)=625 MHz, in good agreement with the experimental value of 647+/-10 MHz. This result suggests that the X (2)Delta ground state of TaO is well described by a pure deltasigma(2) electronic configuration, where the unpaired electron is located in a Ta 5ddelta orbital.