| 1. |
- Céolin, A, et al.
(författare)
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Study of the Dissociation of Nitrous Oxide Following Resonant Excitation of the Nitrogen and Oxygen K-shells
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:2, s. 024306-
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Tidskriftsartikel (refereegranskat)abstract
- A photochemistry study on nitrous oxide making use of site-selective excitation of terminal nitrogen, central nitrogen, and oxygen 1s -> 3 pi excitations is presented. The resonant Auger decay which takes place following excitation can lead to dissociation of the N2O+ ion. To elucidate the nuclear dynamics, energy-resolved Auger electrons were detected in coincidence with the ionic dissociation products, and a strong dependence of the fragmentation pathways on the core-hole site was observed in the binding energy region of the first satellite states. A description based on the molecular orbitals as well as the correlation between the thermodynamical thresholds of ion formation and the first electronic states of N2O+ has been used to qualitatively explain the observed fragmentation patterns.
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| 2. |
- Liu, X. J., et al.
(författare)
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Young's double-slit experiment using core-level photoemission from N-2 : revisiting Cohen-Fano's two-centre interference phenomenon
- 2006
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:23, s. 4801-4817
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Tidskriftsartikel (refereegranskat)abstract
- The core-level photoelectron spectra of N-2 molecules are observed at high energy resolution, resolving the 1 sigma(g) and 1 sigma(u) components as well as the vibrational components in the extended energy region from the threshold up to 1 keV. The sigma(g)/sigma(u) cross section ratios display modulation as a function of photoelectron momentum due to the two-centre interference, analogous to the classical Young's double-slit experiment, as predicted by Cohen and Fano a long time ago. The Cohen-Fano interference modulations display different phases depending on the vibrational excitations in the core-ionized state. Extensive ab initio calculations have been performed within the Hartree-Fock and random phase approximations in prolate spheroidal coordinates. The dependence of photoionization amplitudes on the vibrational states was taken into account using the Born-Oppenheimer approximation. The ab initio results are in reasonable agreement with the experimental data. The theoretical analysis allows the modulation to be connected with the onset of transitions to the states of increasing orbital angular momentum which occurs at increasing photon energies. Deviation from the Cohen-Fano formula is found for both the experimental and the ab initio results and is attributed to electron scattering by the neighbouring atom. A new formula for the interference modulation is derived within the framework of the multiple scattering technique. It differs from the classical Cohen-Fano formula by the addition of twice the scattering phase of the photoelectron by the neighbouring atom. We demonstrate that one can measure directly the scattering phase by fitting our formula to the experimental results.
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| 3. |
- Mucke, Melanie, et al.
(författare)
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Competition of inelastic electron scattering and Interatomic Coulombic Decay in Ne clusters
- 2015
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 200, s. 232-238
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Tidskriftsartikel (refereegranskat)abstract
- The creation of slow electrons due to Interatomic Coulombic Decay of 2s vacancies in Ne clusters is quantitatively compared to the slow electron yield by intracluster electron impact ionization. Using electron-electron coincidence spectroscopy, both channels can be separated experimentally. Two cluster size distributions, corresponding to two and five to six filled solvation shells, are probed.
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| 4. |
- Mucke, Melanie, et al.
(författare)
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Performance of a short "magnetic bottle" electron spectrometer
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 83:6
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a newly constructed electron spectrometer of the magnetic bottle type is described. The instrument is part of an apparatus for measuring the electron spectra of free clusters using synchrotron radiation. Argon and helium outer valence photoelectron spectra have been recorded in order to investigate the characteristic features of the spectrometer. The energy resolution (E/Delta E) has been found to be similar to 30. Using electrostatic retardation of the electrons, it can be increased to at least 110. The transmission as a function of kinetic energy is flat, and is not impaired much by retardation with up to 80% of the initial kinetic energy. We have measured a detection efficiency of most probably 0.6(-0.1)(+0.05), but at least of 0.4. Results from testing the alignment of the magnet, and from trajectory simulations, are also discussed. [http://dx.doi.org/10.1063/1.4729256]
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| 5. |
- Piancastelli, Maria Novella, et al.
(författare)
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A High-resolution Study of Resonant Auger Decay Processes in N2O After Core Electron Excitation from Terminal Nitrogen, Central Nitrogen and Oxygen Atoms to the 3π LUMO
- 2007
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 40:17, s. 3357-3365
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Tidskriftsartikel (refereegranskat)abstract
- Decay spectra of N2O following excitation to the N terminal (Nt) → π*, N central (Nc) → π* and O is → π* intermediate states are reported. The final states reached after participator decay show resonant enhancement consistent with a local-density-of-states analysis based on the Mulliken population of the valence molecular orbitals. In particular, the X-state is resonantly enhanced mostly after excitation from the Nt 1s and the O Is core levels to the π*, while the B-state is mostly enhanced following the excitation of the Nc Is → π* intermediate state. Below the Nt Is threshold, the lowest lying peak related to spectator decay falls at lower binding energy than the highest lying participator peak. This can be attributed to a particularly strong screening effect exerted by the excited electron in the LUMO.
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| 6. |
- Piancastelli, Maria Novella, et al.
(författare)
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Electronic Structure of Core-excited and Core-ionized Methyl Oxirane
- 2007
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 156, s. 259-264
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Tidskriftsartikel (refereegranskat)abstract
- We report a detailed analysis of the electronic structure of methyl oxirane, including core-level photoelectron spectroscopy, X-ray absorption at both C and O K-shells, resonant Auger and normal Auger spectroscopy. The X-ray absorption spectra (XAS) around the C K-edge can be easily interpreted on the ground of the chemical shift between the carbon atoms with different chemical environments. The X-ray absorption data around the O K-edge are quite structureless, hinting for a likely fragmentation process (possibly implying a ring-opening reaction). In resonant Auger spectra obtained after excitation below both the C 1s and O 1s ionization thresholds we notice a predominance of spectator decay implying a strong mixing between empty molecular orbitals and Rydberg states.
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| 7. |
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| 8. |
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| 9. |
- Travnikova, Oksana, et al.
(författare)
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Selective vibrational excitation in the resonant Auger decay following core-to-pi transitions in N2O
- 2010
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 181:2-3, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- In N2O a detailed study of the vibrational distribution of the (X) over tilde state reached after decay of core-to-pi* excitation of N terminal, N central and 0 1s core levels is reported. We observe a change in the relative intensity of bending versus stretching modes while scanning the photon energy across all three resonances. While this effect is known to be due to the Renner-Teller splitting in the core-excited states, we could derive that the antisymmetric stretching is excited mainly in the decay of the N terminal 1s-to-pi* excitation. An explanation for such selectivity is provided in terms of interplay of vibrational structure on potential energy surfaces of different electronic states involved in the process.
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| 10. |
- Ueda, K., et al.
(författare)
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Role of the recoil effect on two-center interference in x-ray photoionization
- 2006
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104 .- 1873-4421. ; 329:1-3, s. 329-337
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectra of the N-2 molecule are studied both experimentally and theoretically in the extended energy region up to 1 keV. The ratio of the photoionization cross sections for the gerade and ungerade core levels displays a modulation in the high energy region caused by the two-center interference, as predicted by Cohen and Fano (CF) in 1966. The physical background of this CF effect is the same as in Young's double-slit experiment. We have found that the interference pattern deviates significantly from the CF prediction. The origin of such a breakdown of the CF formula is the scattering of the photoelectron inside the molecule and the momentum transfer from the emitted fast photoelectron to the nuclei. Usually the recoil effect is small. We show that the electron recoil strongly affects the two-center interference pattern. Both stationary and dynamical aspects of the recoil effect shed light on the role of the momentum exchange in the two-center interference.
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