Ethylene absorption spectrum

Ethylene. The ethylene absorption spectrum has three continua140 with bands superposed. Figure 23 presents the absorption coefficients. The continuum from 1375 to 2000 A. whose maximum lies at about 1620 A. corresponds to the V(Biu) — NQAi,) transition. While the CH2 groups in the ground-state molecule are coplanar, the upper state... 

Fig. 6.2 Absorption spectrum of silver nanoparticles prepared from an aqueous solution (70 ml) of AgN03 (0.2 mM) containing polyethylene glycol (0.1 wt%) and ethylene glycol (0.1 M)...

Another possible source of modification of the HBI optical properties arises from cis-trans (or, more properly, Z-E) isomerization around its exocyclic ethylene bridge (dihedral angle x as depicted in Fig. 3a) [74, 75]. The absorption spectrum of trans HBI in different solvents is red-shifted by 5-10 nm compared to that of the cis conformation [76]. While the trans conformation is thermodynamically unfavorable and contributes only a minor population at room temperature, cis-trans isomerization seems to take place regardless of the chromophore ionization state, and involves a relatively low energy barrier of about 50 kJ/mol [75], a value that appears significantly lower than initially predicted from quantum mechanics [77, 78]. 

One of the preliminary indications which reveals the potential capacity of a material to generate second harmonics is its solvatochromatic behaviour, i.e. the ability of a material to give rise to considerable differences in its UV-visible spectrum on changing solvent. For example, the electronic absorption spectrum of cw-ferrocenyl-2-(4-nitrophenyl) ethylene in dimethylformamide shows two bands at 340 and 492 nm, respectively, whereas in heptane it displays three bands at 320, 406 and 462 nm, respectively. 

Such a process would have an intensity exponent of unity as observed. A further fact in support of the disproportionation mechanism is that the yield of CF2CI2 is largely independent of the ketone pressure at room temperature an abstraction mechanism would require a first-order dependence upon ketone pressure. While the dimer of CF2, tetrafluoro-ethylene, has never been observed in the reaction mixture, a white solid collected in the cell which was probably a polymer of CF2. While the experimental conditions are not strictly comparable, it is significant that the absorption spectrum of CF2 has been observed in the flash photolysis of 1,3-dichlorotetrafluoroacetone.39 When the temperature is raised, however, the yield of CF2C12 in normal photolysis, increases rapidly suggesting an energy of activation and this process can only be chlorine abstraction. The rate function ... 

Ethylene glycol is a very viscous liquid and the molecule presents two close OH groups. It has to be noticed that, among all the different solvents studied by pulse radiolysis, the transition energy of the solvated electron absorption band is maximum in liquid ethylene glycol. For these reasons, the electron in EG seems to have a special behaviour and it is of great interest to study the dynamics of the formation of equilibrated solvated electron. Within this context, the present communication deals with the dynamics of solvation in EG of electrons produced by photoionisation of the solvent at 263 nm. The formation of solvated electrons is followed by pump-probe transient absorption spectroscopy in the visible spectral range from 425 to 725 nm and also in near IR. For the first time, the absorption spectrum of the precursor of the equilibrated electron is observed in EG. Our results are shortly compared by those obtained in water and methanol. 

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 4. Absorption spectrum of ethylene-carbon monoxide (1%) copolymer in heptane at 80°C.

The absorption spectrum for a typical stabilizer of this type, 2-hydroxy-4-dodecyloxybenzophenone, is shown in Figure 8 (10) along with that of poly (ethylene—CO). Over the near ultraviolet range, the absorption coefficient of the stabilizer is much greater than that of the polymer, and even at low concentrations the stabilizer will absorb most of the light, thereby protecting the polymer. 

Nevertheless the correspondence of diborane with ethylene was found from extensive investigations on the infra-red absorption spectrum and the Raman spectrum to be greater than with ethane. There is also a correspondence in the Raman spectrum with A12C16 which is built up of two tetra-hedra with a common edge. 

A solvent which has been foimd to be of great interest in connection with protein conformation studies is ethylene glycol. Sage and Singer (1958, 1962) have investigated in some detail the properties of RNase in pure ethylene glycol, containing added neutral electrolyte. They examined the ultraviolet absorption spectrum, the ionization behavior of the tyrosine residues by spectrophotometric titration experiments, and the optical rotatory dispersion of the system. 

The photolysis of diazirine °° at 3130 A yields ethylene and nitrogen methylene is probably formed in the primary process. The long wavelength absorption ( max = 3200 A) had been identified as the allowed (a, n ) transition and semi-empirical Huckel calculations indicate that the methylene produced must be (Ai) or (Bi). There is evidence that methylene produced from the photolysis of diazirine is more selective than methylene from diazomethane, owing to decreased excess translational energy. At low pressures 5-30 torr, diazomethane was identified as an intermediate by its absorption spectrum and the question arises, is methylene formed directly, or does it arise from decomposition of diazomethane The quantum yield of disappearance of diazirine is 2.0+0.5 and the quantum yield of diazomethane formation is about 0.2. The intermediate diazomethane is... 

---