Photoelektronen‐Spektren von Nichtmetall‐Verbindungen und ihre Interpretation durch MO‐Modelle

Bock, Hans; Ramsey, Brian G.

doi:10.1002/ange.19730851802

Cited by 101 publications

(7 citation statements)

References 133 publications

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“…Of course the above-described methods cannot account for the effects of mixing between different excited electronic configurations. However, the considerable success of calculations based on Koopmans' theorem for the assignment of photoelectron spectra 51 shows that these effects may be absorbed into a one-electron picture if they are not predominant.…”

Section: Resultsmentioning

confidence: 99%

Calculations of the Optical Spectra of Hydrocarbon Radical Cations Based on Koopmans' Theorem

et al. 2007

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The first few bands in the optical spectra of radical cations can often be interpreted in terms of A-type transitions that involve electron promotions from doubly occupied to the singly occupied molecular orbital (SOMO) and/or B-type transition which involve electron promotion from the SOMO to virtual molecular orbitals. We had previously demonstrated that, by making use of Koopmans' theorem, the energies of A-type transitions can be related to orbital energy differences between lower occupied MOs and the highest occupied MO (HOMO) in the neutral molecule, calculated at the geometry of the radical cation. We now propose that the energies of B-type transitions can be related similarly to energy differences between the lowest unoccupied MO (LUMO) and higher virtual MOs in the dication, also calculated at the geometry of the radical cation, by way of an extension of Koopmans' theorem to virtual MOs similar to that used sometimes to model resonances in electron scattering experiments. The optical spectra of the radical cations of several polyenes and aromatic compounds, the matrix spectra of which are known (or presented here for the first time), and for which CASSCF/CASPT2 calculations are available, are discussed in terms of these Koopmans-based models. Then the spectra of five poly(bicycloalkyl)-protected systems and that of hexabenzocoronene, compounds not amenable to higher level calculations, are examined and it is found that the Koopmans-type calculations allow a satisfactory interpretation of most of the features in these spectra. These simple calculations therefore provide a computationally inexpensive yet effective way to assign optical transitions in radical ions. Limitations of the model are discussed.

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Section: Resultsmentioning

confidence: 99%

Calculations of the Optical Spectra of Hydrocarbon Radical Cations Based on Koopmans' Theorem

et al. 2007

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“…temperature in excess of 1000 K! As with other azides,24 this can be carried out safely with small amounts of sample using PE spectroscopic realtime gas analysis.7 Optimization of the N2 extrusion conditions by inspection of the ionization patterns recorded with increasing temperature shows H5C6-Si(N3>3 to be completely desomposed at 1100 K: its strong (7N3-ionization band24 between 15 Figure 9. He I spectra of triazidophenylsilane at 340 K and its pyrolysis products at 1100 K (N2 bands in black).…”

Section: 29si Endor Spectroscopy Of Organosilicon Radical Cationsmentioning

confidence: 99%

“…C(S!R,), ICHj (2£L jSKS*,)F igure15. First vertical ionization energies IEiv(no) (eV) of H2O and its alkyl, silyl, trimethyl, and (trimethylsilyl)methyl derivatives: (--) identical mono-and disubstitution, (• •) alkyl/silyl comparison, and (-• -) /3-silyl substituent effects.…”

mentioning

confidence: 99%

Organosilicon Radical Cations

Bock¹,

Solouki²

1995

Chem. Rev.

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“…A) Newly developed high performance PE spectrometer (type Leybold UPG 200) with separate measuring bench and control panel; the instrument can be connected to a computer, e. g. a PDP 11/40 (32 K), via an interface provided by the manufacturer. B) Details of the ionization chamber with explanation of the working principle: 1. substance inlet, 2. electron impact furnace, 3. ionization chamber (analyzer behind), 4. helium(1) proton source, 5. cold trap, 6. additional turbo pump.…”

Section: Comments On the Instrumentation: Pe Spectrometersmentioning

confidence: 99%

“…In contrast to the electronic excitations in the visible and ultraviolet spectral regions with their selection rules, all single ionizations are usually allowed and therefore observable. A simplifying rule-of-thumbf6' states that in the so-called "helium(1)"-range 6 eV-21 eV the number of observable ionizations should be equal to havthe number of all element p -and hydrogen Is-electrons formally present in the moleculk'61.…”

Section: H-h C = O Hoh Hcohmentioning

confidence: 99%

Photoelectron Spectra and Molecular Properties: Real‐Time Gas Analysis in Flow Systems

Bock

Solouki

1981

Angew. Chem. Int. Ed. Engl.

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Dedicated to Professor Heilbronner on the occasion of his 60th birthdayFor the analysis and optimization of numerous gas phase reactions in flow-systems, photoelectron spectroscopy has proven most valuable. This real-time measuring probe allows one to determine-with millimol quantities and within a few hours-the temperatures for different decomposition channels. Simultaneously, main products are characterized and, if need be, their yield can be improved. By careful performance of the experiment, short-lived and/or reactive molecules such as P2, thioformaldehyde or silabenzene can be detected. PEspectroscopic gas analysis is of particular advantage in the search for heterogeneous catalysts; they can be tested within a day using gas mixtures of varying composition over the temperature range from 300 K to 1300 K. In addition, PE-spectrometers are well-suited for on-line connection to computers; portable instruments for laboratory use are under development."Besser ist's doch wie gar nichts"

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Photoelektronen‐Spektren von Nichtmetall‐Verbindungen und ihre Interpretation durch MO‐Modelle

Cited by 101 publications

References 133 publications

Calculations of the Optical Spectra of Hydrocarbon Radical Cations Based on Koopmans' Theorem

Calculations of the Optical Spectra of Hydrocarbon Radical Cations Based on Koopmans' Theorem

Organosilicon Radical Cations

Photoelectron Spectra and Molecular Properties: Real‐Time Gas Analysis in Flow Systems

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