Electric Dipole Moments of Several Molecules from the Stark Effect
TL;DR: The following molecular electric dipole moments, in Debye units, have been obtained from the Stark effect of pure rotational spectra observed in the microwave region: 0.234±0.004 for NF3, 1.03±0,0.01 for PF3; 1.77± 0.06 for CH3CN; 3.83± 0.,3.00±0.,0.02 for HCN, 3.92± 0,2.
Abstract: The following molecular electric dipole moments, in Debye units, have been obtained from the Stark effect of pure rotational spectra observed in the microwave region: 0.234±0.004 for NF3; 1.03±0.01 for PF3; 1.77±0.02 for POF3; 3.00±0.02 for HCN; 3.92±0.06 for CH3CN; 3.83±0.06 for CH3NC; 1.79±0.02 for CH3F; 0.75±0.01 for CH3CCH; 1.26±0.01 for SiF3H. All values apply to the ground vibrational state.
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TL;DR: In this paper, the distortion moment microwave spectrum of a heavy molecule has been detected for the first time and the molecular structure has been obtained from ground vibronic state microwave data alone.
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TL;DR: In this article, equilibrium structures have been obtained for a variety of mono- and bis-nitriles and some acetylenes, using an ab initio double or triple zeta basis each with polarisation.
Abstract: Equilibrium structures have been obtained for a variety of mono- and bis-nitriles and some acetylenes, using an ab initio double or triple zeta basis each with polarisation. The computed rotation constants are in close agreement with experimental values. The non-linearity of many mono- and bis-nitriles is discussed both for the free molecule and the condensed state. It appears that the CN group bends towards the less electronegative side in planar systems.
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TL;DR: In this paper, Fourier transform microwave spectroscopy of PF3 with Ar and Kr was used to study the force constants and amplitudes of vibration for the van der Waals modes of the complexes and the average moments of inertia and structural parameters.
Abstract: The complexes of PF3 with Ar and Kr, were studied by Fourier transform microwave spectroscopy. The force constants and amplitudes of vibration for the van der Waals modes of the complexes and the average moments of inertia and structural parameters were estimated from the centrifugal distortion constants. The distance (Rc.m. )ave between the rare‐gas atom and the center of mass of PF3 is 3.959 A for the Ar complex and 4.077 A for Kr while the angle (θc.m. )ave between the Rc.m. vector and the C3 axis of the PF3 is 69.30° and 67.25°, respectively. The dipole moments of both complexes and of free PF3 were determined. The induced dipole components estimated for the rare gas using electric fields from ab initio calculations of PF3 agree with the experimental values for a conformation with the rare gas over a PF2 face. The PF2 face conformation is also consistent with the observed and ab initio estimates of the 83 Kr nuclear quadrupole coupling constant for the 83 Kr–PF3 species.
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TL;DR: The molecular force field and polar tensor of methyl isocyanide have been determined from its gas phase vibrational frequencies and infrared intensities and the mean dipole moment derivatives obtained here indicate the correct 1s methyl carbon ionization energy as 293.35 eV which is 0.98 eV higher than the corresponding ionizationEnergy of the terminal atom.
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TL;DR: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier.
Abstract: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier. By using a very narrow band‐width, achieved by employing phase‐sensitive detection, high sensitivity is obtained. The klystron is swept mechanically over the frequency range. Details of the components are given.
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