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91.
92.
Rotational spectra for 14 isotopic species of ethylene ozonide have now been assigned. The consistency of the Kraitchman substitution structure was checked by calculating the Op---Op bond distance six ways; the values ranged from 1.458 to 1.502 Å. This variation was attributed to an amplification of residual vibrational effects by large axes rotations upon isotopic substitution. Estimates of errors produced from this effect were made and a procedure was developed for choosing rs parameters in which the effect is minimized. This gave the following ring parameters: d(COe) = 1.416 Å, d(COp) = 1.412 Å, d(OO) = 1.461 Å, <COeC = 104.8°, <OeCOp = 105.5°, <COpOp = 99.3°. 相似文献
93.
David J. Finnigan Charles W. Gillies Richard D. Suenram E.Bright Wilson Hasse Karlsson 《Journal of Molecular Spectroscopy》1975,57(3):363-376
The microwave spectra of the ground state and several low-lying vibrational modes of 1,3-difluoroacetone have been assigned and analyzed. The assigned form has a molecular conformation in which one fluorine atom lies cis and the other trans to the oxygen atom. The rotational constants of the ground state species were determined using a centrifugal distortion analysis: A = 6024.843 ± 0.006 MHz, B = 2454.414 ± 0.001 MHz, C = 1783.897 ± 0.001 MHz. The molecular dipole moment components of the ground state species lie along the a and b principal axes with μa = 2.38 ± 0.03 D, μb = 0.89 ± 0.03 D, and μT = 2.54 ± 0.03 D. Comparative intensity measurements with OCS microwave lines indicate that the assigned form constitutes only 20% to 30% of the total gas mixture, the remainder presumably consisting of one or more other conformers, perhaps the gauche-gauche form. The lowest vibrational frequency (82 ± 12 cm?1) is attributed to the trans-CH2F torsion, while the next-higher vibrational frequency (127 ± 15 cm?1) is believed to be the cis-torsion. A low-frequency in-plane bending motion is found at 285 ± 25 cm?1. 相似文献
94.
Stephen J. Blunden Andrew Frangou Duncan G. Gillies 《Magnetic resonance in chemistry : MRC》1982,20(3):170-174
Dipole-dipole relaxation via non-bonded protons is an important relaxation mechanism for119Sn in tri-n-propyltin and tri-n -butyltin compounds. This causes a negative nuclear Overhauser effect, arising from the negative magnetogyric ratio, which in some cases nulls the signal. The relative contributions from the spin-rotation and dipole-dipole mechanisms vary: larger molecules have lower spin-rotation and higher dipolar relaxation rates. The practical significance of large nuclear Overhauser enhancement factors in recording 119Sn spectra and the relation of the dipole-dipole contribution to the molecular motion and of the spin-rotation contribution to the absolute shift scale for 119Sn are discussed. 相似文献