Scissoring modes

SO,- 1330-1260 (m-s) 1155-1110 (s) 610-540 (m) 512-485 (m) Asymmetric SO2 stretching Symmetric SO2 stretching Scissoring mode of aryls Scissoring mode of alkyls... 

In the "scissors mode" of H2O, the protons move parallel to the surface and the oscillation frequency is almost unaffected. For NH3, on the other hand, the so called "umbrella mode" is drastically stiffened by the surface because the protons move against the surface and suffer a strong Coulomb repulsion. Here again the dynamical dipole moment is dp/da = 2 Pj, slnda. For NHj, where Pjj = 0.53 a.u., the enhancement of the aynamlc dipole by the surface is compensated by the smaller oscillation amplitude. 

H 0+C0/Rh(111) produced features analogous to those shown for D20+C0/Rh(lll). A partial superposition of the downshifted CO stretch and the H-O-H scissor mode at 1620 cm-1 makes the effect less welI-resolved for H.O than for D 0, but we in fact observed the CO downshift first witn HgO. 

Next are the vibrations in which the bond angle varies periodically but the bond length remains constant. This is called a scissor-mode vibration, because it looks like the action of a pair of scissors, as depicted in Figure 9.22(b). 

Figure 9.22 Simple vibration modes for carbon dioxide, 0=C=0 (a) a symmetric stretching mode and (b) a scissor mode vibration...

Fig. 6.15 The increase in the Si-O-Si vibrational modes (980-1200 cm"1) upon storage of a high porosity (75%) micro PS layer formed on a p-type substrate (0.2 Q cm) in ambient air. The Si—H2 scissors mode (905 cm"1) shows little time dependence. After [Th7],...

Fig. 2. The highest occupied molecular orbital for the scissoring mode.

Scissoring-mode orbital energies are well represented by the expression... 

The vibrational spectrum of LiC2H4 presents some striking similarities to that of ethylene bonded to other metals . The C—C stretching and in-phase CH2 scissoring modes were found to be very strongly IR-activated. The other symmetrical vibrations, CH2 wagging and Li—C stretching motions, were detected at about 700 and 300 cm 48,50 ... 

Note the very close spacing of the interacting or coupled asymmetric and symmetric stretching, above, compared with the far-removed scissoring mode. 

Figure 18 Plot of various modes as a function of temperature in 70 mM SDS + NaCl. a) symmetric CH2 stretching mode b) symmetric S-0 stretching mode c) CH2 scissoring mode.

Fundamental vibrations involve no change in the center of gravity of the molecule. The three fundamental vibrations of the nonlinear, triatomic water molecule are depicted in the top portion of Figure 2.1. Note the very close spacing of the interacting or coupled asymmetric and symmetric stretching compared with the far-removed scissoring mode. 

Fig. 5(d) reveals that the relative intensity of the two bands at 1471 and 1462 cm, assigned to CH2 scissoring modes of non-interdigitated and inter-digitated parts of the alkyl chain, respectively, changes as a function of time. The observation in Fig. 5(d) suggests that the proportion of the interdigitated... 

The IR spectra of DODA/HPA LB films show very strong bands at 2916, 2849 and 1467cm, which are assigned to the stretching and scissoring modes of CH bonds of DODA alkyl chains. The characteristic peaks of HPA are covered up by the strong absorption peaks of the quartz substrate. 

Mendelsohn and Mantsch, 1986). The less intense band at 1470 cm which corresponds to the scissoring mode of CH2 groups, is in some cases useful. Mendelsohn used the rocking mode wavenumbers of selectively deuterated methylene groups to monitor the conformational disorder in bilayers (Mendelsohn, 1991). 

Adsorption of ethylene on Rh(lOO) presaturated with hydrogen produceda TT-bonded species at low temperatures. The degree of sp -to-sp rehybridization upon chemisorption was expressed in terms of a tto parameter derived from the HREEL spectrum via the mixing of the C -C (or C=C) stretch and the CH2 scissor modes. The na parameter, which was normalized to zero for pure sp hybridization (C2H4) and to unity for pure sp hybridization (C2H4Br2), was estimated to be 0.39 for chemisorbed C2H4 in comparison, a jra parameter of 0.38 was obtained for Zeise s salt. The close agreement... 

Figure 7 illustrates the temperature-dependent IR factor group splitting of the alkyl chain CH2 scissoring mode of human SC as a function of... 

Figure 7 (a) Temperature-dependent factor group splitting of the infrared-active, CH2 scissoring mode of human stratum comeum as a function of different hydration (open circle, 0% closed square, 17% open triangle, 33% closed triangle, 70% open square, 300%). (b) The same data plotted on an expanded scale. (From Ref. 40.)... 

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