Photoelectron (He(I), He(II) and X-ray) spectroscopy of γ-pyrone and its related sulphur derivatives: valence and core ionization energies and shake-up satellites |
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Authors: | Francesco Paolo Colonna Giuseppe Distefano Maurizio Guerra Derek Jones |
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Institution: | Laboratorio dei composti del carbonio contenenti eteroatomi e loro applicazioni del Consiglio Nazionale delle Ricerche, Via Tolara di Sotto 89, Ozzano Emilia, Bologna Italy |
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Abstract: | The photoelectron He(I) and He(II) spectra of 4H-pyran-4-one (1), 4H-thiopyran-4-one (2), 4H-pyran-4-thione (3) and 4H-thiopyran-4-thione (4) are reported. The assignments are based on experimental evidence, taking into account the results of theoretical calculations. The outermost orbital sequences proposed (X = O, S) are nX (σ), 3b1 (π), 1a2(π) for 1, 2 and 4; and 3b1(π), nX(σ) and 1a2(π) for 3. The shifts of the core-ionization energy values for 1–4 are ascribed to a drift of π-charge from the intracyclic heteroatom towards the carbonyl or thiocarbonyl group. Low-energy shake-up satellites (up to 25% with respect to the main line) are observed in the various energy regions of the XPS spectra. They are qualitatively reproduced by CNDO/2 calculations. The most important satellites derive from the transition in the ion corresponding to the 3b1 (π) → 4b1(π*) transition in the UV-visible spectra of the neutral molecules. Charge rearrangements accompanying this transition lead to charge depletion of the core-ionized atom. |
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