Twisting vibrations

Fig. 4. Twisting vibration of the two benzene nuclei about the normal axis...

The kinetics of the laser-induced polymerization was followed either by measuring the thickness of the insoluble polymer film formed on the quartz plate after laser exposure and solvent development, using UV spectroscopy or by monitoring the decrease of the IR absorption of the coating at 810 cm-1 which corresponds to the twisting vibration of the acrylate CH2=CH double bond. This last method permits accurate evaluation of the rate of polymerization (Rp) by observing the variation of the 810 cm-1 band, and using Equation 2 ... 

In the Raman spectrum of polyethylene the main peak of the bending vibrations is observed at 1437 cm, while a wagging vibration shows a weak band at 1370 cm and a twisting vibration gives a strong band at 1295 cm The stretching vibrations of the C-C chain are observed at 1126 and 1059 cm, respectively, in the Raman spectrum (Figs. 4.1-2A and 4.1-3). A normal coordinate calculation of polyethylene is published by Tasumi et al. (1962). 

Subscript w means that the times were determined in the range of the linear part of the l/i (r/Tj) dependence at high T/tj > (1 - 2) x 10 K/P l/i is the parameter reflecting the contribution of the amplitude of high-frequency twisting vibrations in the unit with LM to the change in PL of the solution of the polymer with LG. 

The enthalpy of hydrogen bond in cyclic dimers (Fig. 20a) in the ABA and AOBA is equal to —35.3 0.8 kJ/mol per hydrogen bond at T 300 K. For the quantitative estimation of the enthalpy the Iogansen method [296] has been applied, which is based on the analysis of the shift of the frequency of twisting vibration pOH and that of the gravity center of the Voh band of associates with relation to the corresponding shifts for monomers. The determination of frequencies pQ on and of ABA and AOBA monomers, which are needed... 

Fig. 4.18. Potential function determined for the ring-twisting vibration in 1,3-cyclohexadiene. [Reproduced from Carreira, L. A., Carter, R. 0., Durig, J. R. J. Chem. Phys. 59,...

C-H rocking and twisting vibration of CH2 groups in long chain acids ... 

The low frequency of V2 (C-C) and the prominence and very low frequency of the twisting vibration indicate that the positive ion is twisted in its ground state, so that the two CH2 groups are no longer in the same plane (see below). 

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