Butadienes, photoionization

In this contribution, in order to illustrate tlie importance of shake-up bands for extended systems, we simulate and compare on correlated grounds the ionization spectra of polyethylene and poly acetylene, the most simplest systems one can consider to represent insulating or semi-conducting polymers. Conclusions for the infinite stereoregular chains are drawn by exU apolation of the trends observed with the first terms of the related n-alkane or acene series, CnH2n+2 and CnHn+2. respectively, with n=2, 4, 6 and 8. Our simulations are also compared to X-ray photoionization spectra (7) recorded on gas phase samples of ethylene, butadiene and hexatriene, which provide a clear experimental manisfestation of the construction of correlation bands (8-12). 

An excellent agreement with the X-ray photoionization spectra of ethylene, butadiene and hexatriene (7) is obtained (12) (Figure 3) when including in our calculations the Gelius (36) photoionization cross sections for an Alka photon beam, by means of Eqs. (4) and (5). Such a direct comparison is impossible for octatetraene, a compound for which there is no available XPS data. 

Figure 3 Hie simulated ADC[3] X-ray (AlKa) photoionization spectra (full lines) of (a) ethylene, (b) butadiene and (c) hexatriene versus the conesponding experimental records (dotted lines) by MJ. Keane et al... 

FIGURE 31. He(I) photoelectron spectrum of 1,3-butadiene (upper figure) and photoelectron/photoion coincidence spectra of various fragment ions. The yield of ion is indicated on the scale 0 to 1.0 °... 

Zoller, D.L. and Johnston, M.V., Composition and Microstructure of Acrylonitrile-Butadiene Copolymers by Pyrolysis-Photoionization Mass Spectrometry, Anal Chem, 69, 3791 (1997). 

Rate constants measured for the reactions in 1,3-butadiene are given in Table I and compared with those measured by Barber et for reactant ions produced by electron impact. It is seen that the agreement between the two sets of rate constants is only fair, even if a correction factor is applied so that both quantities are made equal for one reaction. If the discrepancy is outside experimental error, it may have a very interesting origin. It should be remembered that the internal-energy distribution of the reactant ions produced by photoionization extends only to 10.19 eV - /, whereas the internal-energy distribution of ions produced by electron impact can extend up to the dissociation limit of the reactant... 

Fig. 10.12. Pyrolysis-photoionization mass spectrum of acrylonitrile-butadiene copolymer (a) additives at 200°C, and (b) pyrolysis products for the 30-32% acrylonitrile copolymer at 275°C. (Source Ref. [57,...

Fig. 10.13. Pyrolysis-photoionization mass spectra expanded in the octamer region for acrylonitrile-butadiene copolymers with compositions of (a) 19-22%, (b) 30-32%, (c) 37-39%, and (d) 51%. (Source Ref. [57, flg. 3].)...

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