Photoionization calculated

Fig. 10. Comparison of Scofield s calculated x-ray photoionization cross-sections relative to that for F 1 electrons and experimental values (22) as a...

J. H. Scofield. J. Electron Spect. 8,129, 1976. This is the standard quoted reference for photoionization cross sections at 1487 eV. It is actually one of the most heavily cited references in physical science. The calculations are published in tabular form for all electron level of all elements. 

Si 2p line, at about 100 eV BE, is also easily accessible at most synchrotron sources but cannot, of course, be observed using He I and He II radiation. On the other hand, the Zn 3d and Hg 4f lines can be observed quite readily by He I radiation (see Table 1) and the elements identified in this way. Quantitative analysis using relative peak intensities is performed exactly as in XPS, but the photoionization cross sections a are very different at UPS photon energies, compared to A1 Ka energies, and tabulated or calculated values are not so readily available. Quantitation, therefore, usually has to be done using local standards. 

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. 

A possible role for shape resonances has been postulated in a number of the photoionization studies mentioned above [52, 53, 57, 60], although it has to be noted that except for camphor [57], the evidence for the existence of the shape resonance is not definitive. (It also then remains an open question how any such resonances, inferred from fixed geometry calculations, would manifest themselves in practice in large, and sometimes floppy, molecules, such as these chiral species.)... 

Magnesium Photoionization a K-Matrix Calculation with GTO Bases... 

Magnesium photoionization a K-matrix calculation with GTO bases R. Moccia and P. Spizzo... 

Figure 13. Phase lag between the photoionization and photodissociation of vinyl chloride resulting from the Gouy phase of the focused laser beam. The dashed curve shows the results of the analytical model discussed in the text, and the solid curve is a numerical calculation of the phase lag without adjustable parameters.

One rather unfortunate aspect of the M + hydrocarbon (and M + OX) reactions mentioned thus far is that the products of the reactions were not detected directly, but were instead inferred via the pressure and temperature dependencies of the measured rate constants for metal reactant consumption and by comparison to ab initio calculations. Exceptions are the reactions of Y, Zr + C2H4 and C3H6, for which the Weisshaar group employed the 157 nm photoionization/mass spectrometry technique to identify the products of the reaction as those resulting from bimolecular elimination of H2.45 47 95... 

Detailed structural calculations have been carried out for this system. This is because the neutral isomer, C2HsO, which is implicated in the thermochemistry of ethanol, is of interest in pollution control, atmospheric chemistry, and combustion. Also, there is new information available from photoionization experiments with which to compare theoretical calculations. For details of these comparisons, see Curtiss et al.73 In the earlier theoretical studies of Nobes et al.,74 calculations were performed at the MP2 and MP3 levels with basis sets of double plus polarization (6-13G ) with electron correlation. These studies revealed four stable minima for the system protonated acetaldehyde, CHj-C H-OH <-> CH3-CH=0+H the methoxymethyl cation, CH3OCH2 protonated oxirane, (CH2)2OH+ and vinylox-... 

Scofield s calculated X-ray photoionization cross sections, 24 86-87 Scoping activities, EIA, 20 234 Scoping methods, EIA, 20 239t Scopolamine, 2 79, 80 Scopolanine hydrobromide, 4 360t Scorch behavior, in rubber compounding, 22 794... 

Despite many synthetic efforts no P- or As-cluster cations have been characterized in condensed phases to date, although their existence in the gas phase is well established by mass spectrometry and photoionization in combination with quantum chemical calculations (see below). Only one antimony cation is claimed in con-... 

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