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  • Articles: DFG German National Licenses  (21)
  • Electronic Resource  (21)
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  • Articles: DFG German National Licenses  (21)
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  • Electronic Resource  (21)
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  • 1
    Electronic Resource
    Electronic Resource
    Electronic transitions of cobalt carbide, CoC, near 750 nm: A good example of case (bβS) hyperfine coupling (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 8360-8371 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The laser induced fluorescence spectrum of jet-cooled CoC near 750 nm has been measured at high resolution following the reaction of laser-ablated cobalt atoms with methane. The X2Σ+ ground state of CoC is an unusually good example of Hund's case (bβS) coupling. Since Co has a nuclear spin I=7/2, each rotational level is split by the Fermi contact interaction into G=3 and G=4 components, where G=I+S; the splitting for N=0 is more than 0.5 cm−1. The X2Σ+ state begins to uncouple toward case (bβJ) with increasing rotation. Transitions to various 2Π excited states occur in the region 13 000–14 500 cm−1; the most prominent of these (for which high resolution spectra have been recorded) lie at 13 079 cm−1 (2Π3/2) and 13 343 cm−1 (2Π1/2). The (bβS) coupling in the ground state produces some unexpected hyperfine intensity patterns, which have been studied in detail. A very low-lying 2Δi state, whose Ω=5/2 and Ω=3/2 components lie at 221 and 1173 cm−1, has been identified. Laser excitation of the 2Π3/2–2Δ5/2 transition has been observed by monitoring the strong 2Π3/2–X2Σ+ emission, which has allowed the 2Δ5/2 state to be characterized at high resolution. A total of 879 rotational-hyperfine transitions between the various 2Π1/2, 2Π3/2, 2Δ5/2, and 2Σ+ states have been assigned and fitted. Matrix elements for a 2Σ+ state in case (bβS) coupling are listed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470148
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  • 2
    Electronic Resource
    Electronic Resource
    Hyperfine structure in high spin multiplicity electronic states: Analysis of the B 4Π–X 4Σ− transition of gaseous NbO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6240-6262 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The (0,0) band of the B 4Π–X 4Σ− transition of NbO, near 6600 A(ring), has been analyzed from spectra taken at sub-Doppler resolution. The transition is notable for the great width of its Nb nuclear hyperfine structure, which is caused principally by the unpaired 5sσ electron in the ground state interacting with the large magnetic moment of the 4193Nb nucleus (I=9/2). A fit to the ground-state combination differences, including four very precise microwave lines measured by Suenram et al. [J. Mol. Spectrosc. 148, 114 (1991)], has given a comprehensive set of rotational, spin, and hyperfine parameters. Prominent among these are the third-order spin–orbit distortions of the spin-rotation interaction and the Fermi contact interaction, which are large and well determined, reflecting different degrees of spin–orbit contamination of the the 4Σ1/2− and 4Σ3/2− components of the ground state.The δ 2π B 4Π state was hard to fit, for a number of reasons. First, its spin–orbit structure is asymmetric, because of strong perturbations by a 2Π state which has been identified in this work, from among the various weak bands in the NbO spectrum near 7000 A(ring); the result is that many high order centrifugal distortion terms are needed in an effective Hamiltonian model for the rotation. Second, the hyperfine structure is perturbed, not only by this 2Π state, but by distant Σ and Δ states at higher energy. The δ 2σ* C 4Σ− state at 21 350 cm−1 appears to be one of these. The distant states generate large apparent nuclear spin-rotation interactions, both within and between the Λ components of the Π state, as a result of cross terms between matrix elements of the operators −2BJ⋅L and aI⋅L. Similar cross terms arising from the operators AL⋅S and aI⋅L produce corrections to the Fermi contact matrix elements and are responsible for the unexpected negative sign of the magnetic hyperfine parameter d. The "off-diagonal'' quadrupole parameter e2Qq2 is very large, and causes some of the higher J line shapes of the B–X system to be noticeably asymmetric at Doppler limited resolution; its value is consistent with the electron configuration of the B 4Π state being δ 2π.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467087
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  • 3
    Electronic Resource
    Electronic Resource
    The near infrared electronic spectrum of tungsten methylidyne, WCH (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6168-6182 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The laser excitation spectrum of tungsten methylidyne, WCH, has been recorded in the 12 000–15 400 cm−1 region. A total of 14 vibronic bands of WCH and 16 bands of WCD have been observed in this region. Rotational analysis shows that the ground state is X˜3/2(2Δ), with the substitution structure r0(W≡C)=1.73665 A(ring) and r0(C–H)=1.0765 A(ring). The excited vibronic levels have been assigned, on the basis of their WCH/WCD isotope shifts and their wavelength resolved fluorescence patterns, to three electronic states, A˜3/2(2Δ), B˜1/2(2Π), and C˜5/2(2Φ), at 12 090, 13 392, and 14 110 cm−1, respectively. The wavelength resolved fluorescence spectra have also established the low-lying vibrational levels of the ground state. The ground state bending fundamental lies at 660 cm−1, while the W–C stretching frequency is 1006 cm−1; the corresponding frequencies in WCD are 501 cm−1 and 953 cm−1, respectively. No evidence for the C–H stretching frequency has been found. Emission has also been observed to a low-lying electronic state, 813 cm−1 above the X˜3/2 state. The pattern of rotationally resolved emission to this state clearly indicates that it is a 4Σ1/2 state. Its bending frequency is 612 cm−1, and its W–C stretching frequency is 971 cm−1, indicating a slightly longer bond length than in the X˜3/2 state. High resolution cw laser spectra of the (0,0) bands of the two lowest excited electronic states [A˜3/2(2Δ) and B˜1/2(2Π)] reveal a small splitting of the four principal tungsten isotopes (182W, 183W, 184W, and 186W) which serves to confirm the presence of tungsten in the carrier. Hyperfine splitting associated with the 183W nucleus (I=1/2) has been observed for the (0,0) band of the A˜3/2−X˜3/2 system, allowing the electron configuration of the ground state to be elucidated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472502
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  • 4
    Electronic Resource
    Electronic Resource
    Sub-Doppler spectroscopy of thioformaldehyde: Excited state perturbations and evidence for rotation-induced vibrational mixing in the ground state (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 7300-7310 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution intracavity dye laser spectroscopy has been used to obtain sub-Doppler spectra of transitions to 350 rotational levels in the 410 band of the A˜ 1A2–X˜ 1A1 electronic transition of thioformaldehyde. Ground state combination differences from the sub-Doppler spectra, combined with microwave and infrared data, have been used to improve the ground state rotational and centrifugal distortion constants of H2CS. The upper state shows a remarkable number of perturbations. The largest of these are caused by nearby triplet levels, with matrix elements of 0.05–0.15 cm−1. A particularly clear singlet–triplet avoided crossing in Ka' = 7 has been shown to be caused by interaction with the F1 component of the 3162 vibrational level of the a˜ 3A2 state. At least 53% of the S1 levels show evidence of very small perturbations by high rovibronic levels of the ground state. The number of such perturbations is small at low J, but increases rapidly beyond J=5 such that 40%–80% of the observed S1 levels of any given J are perturbed by ground state levels. Model calculations show that the density and J dependence of the number of perturbed levels can be explained if there is extensive rotation-induced mixing of the vibrational levels in the ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468287
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  • 5
    Electronic Resource
    Electronic Resource
    Rotational analysis of the A˜ ← X˜ system of C2Hf a@f ) (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 3479-3486 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Precise frequencies for the observed lines of five bands of the A˜ 2Π ← X˜ 2Σ system of C2H are reported. These frequencies have been least-squares fitted with an effective rotational Hamiltonian and the resulting parameters are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448927
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  • 6
    Electronic Resource
    Electronic Resource
    The microwave spectrum of CuO, X 2Π, measured with optical detection (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4754-4761 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave pure rotational transitions J=3/2←1/2 and 5/2←3/2 have been measured for gas phase CuO in its X 2Π state, using microwave-optical double resonance. The copper hyperfine structure was observed, and has been analyzed for the first time for the ground state of an orbitally degenerate transition metal-containing molecule in the gas phase. Rotational, lambda-doubling, and magnetic and electric hyperfine parameters have been evaluated; the Fermi contact parameter bF has been found to be very large and negative. The problem of determining the signs of the "off-diagonal'' hyperfine parameters in 2Π electronic states is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452696
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  • 7
    Electronic Resource
    Electronic Resource
    Intensity cancellation effects in the hyperfine structure of molecules with large nuclear spins: The 6500 A(ring) system of NbO (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1219-1224 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetic hyperfine structure of certain low-JQ lines in the optical spectrum of NbO shows an unusual intensity cancellation effect. In contrast to the normal pattern that ΔF=ΔJ hyperfine components are the strongest, the intensities of the ΔF=ΔJ components are found to pass through zero near the center of the range of F values. Although this effect is implicit in the intensity formulas for the quadrupole hyperfine structure of microwave lines, it seems not to have been noted in published spectra because of the unusual circumstances required for its appearance: a nuclear spin of at least I=5/2 is needed, and only Q lines show it. A classical vector model is presented for its interpretation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452744
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  • 8
    Electronic Resource
    Electronic Resource
    Erratum: Rotational analysis of the A˜ ← X˜ system of C2H [J. Chem. Phys. 82, 3479 (1985)] (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 4278-4278 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449873
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  • 9
    Electronic Resource
    Electronic Resource
    A laser-induced fluorescence study of bands of the red system of gaseous CoO: Evidence for a 4Δi ground state (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 5231-5238 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Three bands of the "red'' system of gaseous CoO have been rotationally analyzed using laser-induced fluorescence techniques. The available evidence indicates that the lower levels are the Ω=7/2 and 5/2 spin–orbit components of a 4Δi electronic state, which is assigned as the ground state of the molecule. The cobalt nuclear hyperfine splittings are small in the ground state, which suggests that no unpaired electron in a σ molecular orbital derived from the Co 4s atomic orbital is present, so that the electron configuration is presumably σ2δ3π2; the ground state bond length (r0) is 1.631 A(ring). The upper electronic levels are heavily perturbed, both rotationally and vibrationally, and their hyperfine structures, though following case (a) behavior, are large and irregular. This work on CoO completes the determination of the ground state symmetries and bond lengths for the whole series of the 3d transition metal monoxides; some comparisons for the members of the series are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452599
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  • 10
    Electronic Resource
    Electronic Resource
    Hyperfine and spin–orbit structure of the 4Δi ground state of CoO (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6336-6344 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A detailed examination of the structure of the 4Δi ground state of gaseous CoO has been carried out from analysis of the electronic spectrum near 6300 A(ring), using intracavity dye laser and wavelength-resolved fluorescence methods. The intracavity experiments have given the details of the hyperfine structure of the two lowest spin–orbit components at sub-Doppler resolution, permitting the hyperfine parameters, a=0.02295 cm−1 and (b+c)=−0.01117 cm−1, to be derived; from the negative value of the contact interaction the electron configuration is established as (4sσ)2(3dδ)3(3dπ)2. The wavelength-resolved fluorescence experiments have given the relative positions of the four spin–orbit components of the X 4Δi state to ±0.3 cm−1. Based on these measurements, a pair of subbands sharing a common electronic upper level, but with the Ω=5/2 and 7/2 components of the ground state as lower levels, has been recognized. Rotational analysis of Doppler-limited intracavity spectra of these two subbands has given an accurate value for the Ω=5/2–7/2 separation as 304.321±0.007 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465872
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