The optical spectrum of diatomic ZrF has been investigated, with transitions recorded in the range from 14,700 to 18,000 cm(-1). Many bands have been observed, several of which can be grouped into three band systems. Rotationally resolved investigations are hampered by perturbations that are rampant among the excited states, but three unperturbed bands have revealed that the ground state of ZrF has Ω" = 3/2, with a bond length of r(e)'' = 1.854(1) Å. Hot bands originating from v" = 1 provide the ground state vibrational interval, ΔG(1/2)'' = 691.45(2) cm(-1) for (90)Zr(19)F. Based on comparisons to ZrCl and ligand-field considerations, the ZrF ground state is assigned as a (2)Δ(3/2) level deriving from the 3σ(2) 1δ(1) configuration, in agreement with a previous study. In addition to the measurements on ZrF, vibronically resolved spectra of ZrCl have been recorded over the 13,000 to 18,000 cm(-1) range, and four band systems have been identified.

Gas phase infrared spectroscopic investigations of the CO vibration of jet-cooled NiCO, Ni(CO)3(13CO), and Ni(CO)3(C18O) are reported. The spectra were obtained using a recently assembled pulsed-discharge slit-jet IR diode laser spectrometer. The rotationally resolved spectrum of NiCO was collected as it was formed in the discharge, while the spectra of Ni(CO)3(13CO) and Ni(CO)3(C18O) were recorded as they were destroyed. For NiCO, band origins of 2010.692 89(34) and 2010.645 28(23) cm(-1) were measured, along with values of B0=0.151 094(7) and 0.149 597(6) cm(-1) and B(1)=0.150 244(7) and 0.148 742(6) cm(-1) for 58NiCO and 60NiCO, respectively. The B0 values for these isotopologs were used to determine the two bond lengths in NiCO, giving r0 (Ni-C)=1.641(40) A and r0 (C-O)=1.193(53) A, in agreement with recent microwave measurements. The constants determined for Ni(CO)3(13CO) were upsilon0=2022.075 753(95) cm(-1), B"=0.034 736(2) cm(-1), and B'=0.034 688(2) cm(-1). For Ni(CO)3(C18O), upsilon0=2021.936 83(18) cm(-1), B"=0.033 764(4) cm(-1), and B'=0.033 710(4) cm(-1) were obtained. From these rotational constants, bond lengths of r0 (Ni-C)=1.839+/-0.007 A and r0 (C-O)=1.121+/-0.010 A were obtained. These values are discussed in relation to the bond lengths measured by electron and x-ray diffraction methods.

The spectra of diatomic PdSi have been investigated for the first time, using the technique of resonant two-photon ionization spectroscopy. A number of vibronic transitions have been observed in the 20,400-22,000 cm(-1) range. It is difficult to group the bands into band systems, although one likely band system has been identified. Three bands have been rotationally resolved and analyzed, two of which are perturbed by interactions with other states. The data show that the ground state of PdSi has Ω = 0, and a bond length of r(0)('') = 2.0824(3) Å. Comparisons to previously published density functional theory calculations provide strong support for the assignment of the ground state to the 1σ(2) 2σ(2) 1π(4) 1δ(4) 3σ(2), (1)Σ(+) term, which is predicted to be the ground state in the calculations. The much shorter bond length and greater bond energy of PdSi, as compared to its isoelectronic counterpart, AlAg, demonstrate that there is strong π bonding in PdSi, as has been previously found for the other nickel group silicides, NiSi and PtSi.