Ethylene vibrational spectra

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 ... 

Ethylene contains six atoms and therefore has 12 possible lines in its vibrational spectrum [(3 x 6) - 6 = 12]. However it is a molecule with relatively high symmetry... 

Figure 6. a) SFG spectrum of the Pt(lll) surface during ethylene hydrogenation with 100 Torr Hj, 35 Torr 615 Torr He at 295 K b) The vibrational spectrum of the same system after the evacuation of the reaction cell c) SFG spectrum under the same conditions as a), but on a surface which was pre-covered in UHV with 0.52 monolayers of ethylidyne. 

Fig. 22. High-resolution electron energy loss vibrational spectrum of ethylidyne (CCHj) and ethylidyne-rfj on Rh(lll) the stable, room temperature, chemisorbed structure for ethylene...

This general behaviour is characteristic of type A, B and C bands and is further illustrated in Figure 6.34. This shows part of the infrared spectrum of fluorobenzene, a prolate asymmetric rotor. The bands at about 1156 cm, 1067 cm and 893 cm are type A, B and C bands, respectively. They show less resolved rotational stmcture than those of ethylene. The reason for this is that the molecule is much larger, resulting in far greater congestion of rotational transitions. Nevertheless, it is clear that observation of such rotational contours, and the consequent identification of the direction of the vibrational transition moment, is very useful in fhe assignmenf of vibrational modes. 

Anti-Stokes picosecond TR spectra were also obtained with pump-probe time delays over the 0 to 10 ps range and selected spectra are shown in Figure 3.33. The anti-Stokes Raman spectrum at Ops indicates that hot, unrelaxed, species are produced. The approximately 1521 cm ethylenic stretch Raman band vibrational frequency also suggests that most of the Ops anti-Stokes TR spectrum is mostly due to the J intermediate. The 1521 cm Raman band s intensity and its bandwidth decrease with a decay time of about 2.5 ps, and this can be attributed the vibrational cooling and conformational relaxation of the chromophore as the J intermediate relaxes to produce the K intermediate.This very fast relaxation of the initially hot J intermediate is believed to be due to strong coupling between the chromophore the protein bath that can enable better energy transfer compared to typical solute-solvent interactions. ... 

Absorption spectra of peridinin in different solvents are shown in Fig. 2a. In the nonpolar solvent M-hexane, the absorption spectrum exhibits the well-resolved structure of vibrational bands of the strongly allowed S0-S2 transition with the 0-0 peak located at 485 nm. In polar solvents, however, the vibrational structure is lost and the absorption band is significantly wider. In addition, there are also differences between the various polar solvents. Although the loss of vibrational structure is obvious, a hint of shoulder is still preserved in methanol and acetonitrile, but in ethylene glycol and glycerol the absorption spectrum is completely structureless with a broad red tail extending beyond 600 nm. 

Figure 3. Overtone and combination band spectrum oj ethylene and water adsorbed on Mn"A zeolite. The ethylene bands lie close to the gaseous (V -f- vn), (vt + vs), 2vlu and 2vs vibrational modes, indicating that the ethylene molecule has retained its chemical composition and structural integrity (-, 1) MnA 4- ethylene (-------------------,2) MnA hydrated CtHt (g) bands.

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