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  • 1
    Electronic Resource
    Electronic Resource
    New measurements of microwave transitions in the water dimer (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6290-6299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: New measurements of ten K=1 lines, including six Q type and four R type, were made on the completely protonated species of the water dimer. For some of these lines, as well as for some K=0 transitions known from the literature, Stark coefficients were determined, and these Stark coefficients provide a confirmation of the assignments. The new K=1 measurements show that the splitting associated with the (HF)2-like tunneling motion decreases from about 19.5 GHz for K=0 to about 16.2 GHz for K=1. To understand the fact that K=1 lines are populated in our 1 K beam, we must assume, in accordance with the results of beam studies on other molecules, that levels of different nuclear spin modification relax separately. In an attempt to gain information on tunneling splittings other than that caused by the (HF)2-like motion, we have made new measurements on 1–0 and 2–1 transitions with K=0 for several partially deuterated species, in which the (HF)2-like motion cannot occur. Small splittings ranging from 4 to 145 MHz were observed. Because of the nature of the tunneling motions involved, these new data yield only the difference of the tunneling splitting in the upper and lower states of the transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453458
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared and microwave investigations of interconversion tunneling in the acetylene dimer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6028-6045 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A sub-Doppler infrared spectrum of (HCCH)2 has been obtained in the region of the acetylene C–H stretching fundamental using an optothermal molecular-beam color-center laser spectrometer. Microwave spectra were obtained for the ground vibrational state using a pulsed-nozzle Fourier transform microwave spectrometer. In the infrared spectrum, both a parallel and perpendicular band are observed with the parallel band being previously assigned to a T-shaped C2v complex by Prichard, Nandi, and Muenter and the perpendicular band to a C2h complex by Bryant, Eggers, and Watts. The parallel band exhibits three Ka=0 and three asymmetry-doubled Ka=1 series. The transitions show a clear intensity alternation with Kc with two of the Ka=0 series missing every other line. In addition, the perpendicular band has the same ground-state combination differences as the parallel band. To explain these apparent anomalies in the spectrum, we invoke a model consisting of a T-shaped complex with interconversion tunneling between four isoenergetic hydrogen-bonded minima. In this picture, the parallel and perpendicular bands arise from excitation of the acetylene units parallel and perpendicular to the hydrogen bond. The observation of rotation–inversion transitions in the microwave spectrum, in addition to the pure rotation transitions of Prichard, Nandi, and Muenter, verifies the model. The measured microwave splittings yield a tunneling frequency of 2.2 GHz which is consistent with a ∼33 cm−1 barrier separating the four minima.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455417
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    P-type doubling in the infrared spectrum of NO–HF (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2992-3004 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The HF stretching band of the NO–HF open-shell complex has been recorded using a molecular-beam optothermal spectrometer. The spectrum exhibits P-type doubling indicative of an unpaired electron spin coupled to the rotational angular momentum of a bent complex with substantially quenched electron orbital angular momentum. From B¯‘=0.111 320(17) cm−1, and an off-axis angle for the NO of 30°, the zero-point center-of-mass separation is estimated to be 3.4396(3) A(ring). The HF frequency shift of 84 cm−1 indicates that the complex is hydrogen bonded, and the spectral intensities imply that the HF axis is aligned closely to the center-of-mass axis and the NO is off axis by 30±15°. The Renner–Teller-like orbital quenching parameter is somewhat larger than the spin–orbit constant in the free NO molecule and increases substantially upon vibrational excitation. The transitions in this band exhibit vibrational predissociation broadening of 200±40 MHz (FWHM), similar to that observed for a number of closed-shell hydrogen-bonded HF complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458886
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    Paper (German National Licenses)
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