A resonant two-photon ionization study of the jet-cooled RuC molecule has identified the ground state as a Σ+1 state arising from the 10σ211σ25π42δ4 configuration. The Δi3 state arising from the 10σ211σ25π42δ312σ1 configuration lies very low in energy, with the Δ33 and Δ23 components lying only 76 and 850 cm−1 above the ground state, respectively. Transitions from the X 1Σ+, Δ33, and Δ23 states to the Π23, Π13, Φ33, Φ43, Φ31, and Π11 states arising from the 10σ211σ25π42δ36π1 configuration have been observed in the 12 700–18 100 cm−1 range, allowing all of these states to be placed on a common energy scale. The bond length increases as the molecule is electronically excited, from r0=1.608 Å in the 2δ4, X 1Σ+ state, to 1.635 Å in the 2δ312σ1, Δ3 state, to 1.66 Å in the 2δ36π1, Π3 and Φ3 states, to 1.667 Å in the 2δ36π1, Φ1 and 1.678 Å in the 2δ36π1, Π1 state. A related decrease in vibrational frequency with electronic excitation is also observed. Hyperfine splitting is observed in the 2δ312σ1, Δ33 state for the Ru99(I=5/2)12C and Ru101(I=5/2)12C isotopic combinations. This is analyzed using known atomic hyperfine parameters to show that the 12σ orbital is roughly 83% 5sRu in character, a result in good agreement with previous work on the related RhC and CoC molecules.

Dispersed fluorescence studies of the diatomic molecules MoC, RuC, and PdC are reported. New states identified in MoC and RuC are the […]2δ112σ1, 3,1Δ2 states and the […]2δ312σ1, 1Δ2 state, respectively. Five states are observed by dispersed fluorescence in PdC. The ground state is found to be […]2δ412σ2, 1Σ+, with the […]2δ412σ16π1, 3ΠΩ manifold of states lying about 2500 cm−1 above the ground state. The [17.9]Ω=1 state of PdC is also identified as […]2δ412σ113σ1, 3Σ+(Ω=1), corroborating recent results of resonant two photon ionization spectroscopy studies. The spin-orbit interactions of these molecules are analyzed to deduce the composition of the molecular orbitals, and comparisons are made to ab initio theory when possible. An examination of the trends in bond energy, bond length, and vibrational frequency among the 4d transition metal carbides is also provided.

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Vibronically resolved resonant two-photon ionization and dispersed fluorescence spectra of the organometallic radicals CrC(2)H, CrCH(3), and NiCH(3) are reported in the visible and near-infrared wavelength regions. For CrC(2)H, a complicated vibronic spectrum is found in the 11 100-13 300 cm(-1) region, with a prominent vibrational progression having omega(e) (')=426.52+/-0.84 cm(-1), omega(e) (')x(e) (')=0.74+/-0.13 cm(-1). Dispersed fluorescence reveals a v(")=1 level of the ground state with DeltaG(1/2) (")=470+/-20 cm(-1). These vibrational frequencies undoubtedly pertain to the Cr-C(2)H stretching mode. It is suggested that the spectrum corresponds to the A (6)Sigma(+)<--X (6)Sigma(+) band system, with the CrC(2)H molecule being linear in both the ground and the excited state. The related CrCH(3) molecule displays a vibronic spectrum in the 11 500-14 000 cm(-1) region. The upper state of this system displays six sub-bands that are too closely spaced to be vibrational structure, but too widely separated to be K structure. It is suggested that the observed spectrum is a (6)E<--X (6)A(1) band system, analogous to the well-known B (6)Pi<--X (6)Sigma(+) band systems of CrF and CrCl. The ground state Cr-CH(3) vibration is characterized by omega(e) (")=525+/-17 cm(-1) and omega(e) (")x(e) (")=7.9+/-6 cm(-1). The spectrum of NiCH(3) lies in the 16 100-17 400 cm(-1) range and has omega(e) (')=455.3+/-0.1 cm(-1) and omega(e) (')x(e) (')=6.60+/-0.03 cm(-1). Dispersed fluorescence studies provide ground state vibrational constants of omega(e) (")=565.8+/-1.6 cm(-1) and omega(e) (")x(e) (")=1.7+/-3.0 cm(-1). Again, these values correspond to the Ni-CH(3) stretching motion. (c) 2004 American Institute of Physics.

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ABSTRACT:The results of an ab initio study on a family of hydroxy peroxy radicalwater complexes formed from the oxidation of E-2-hexenal, which constitutes an important component of biogenic atmospheric emissions, are reported. Binding energies for the b-hydroxy-c-peroxy hexanal (b-and c-positions are relative to the carbonyl) radical-water complex and the c-hydroxy-b-peroxy hexanal radical-water complex are predicted to be to 3.8 and 3.6 kcal/mol, respectively, computed at the MP2/6-311þþG(2d,2p)//B3LYP/ 6-311þþG(2d,2p) computational level. Natural bond orbital reveals that conventional hydrogen bonding between the water and the hydroxy and aldehyde functional groups of the radical are primarily responsible for the stability of the complex. It can be shown that the peroxy moiety contributes very little to the stability of the radical-water complexes. Thermochemistry calculations reveal estimated equilibrium constants that are comparable to those recently reported for several hydroxy isoprene radical-water complexes. The results of this report suggest that the hexanal peroxy radical-water complexes are expected to play a significant role in the complex chemistry of the atmosphere.